# mypy: disallow-untyped-defs import collections import dataclasses import functools import itertools import logging import math import operator import os import pprint import textwrap import typing from typing import ( Any, Counter, DefaultDict, Dict, Generic, List, Optional, Sequence, Set, Tuple, TypeVar, Union, ) import sympy import torch import torch._inductor.async_compile # noqa: F401 required to warm up AsyncCompile pools from torch._dynamo.utils import counters, dynamo_timed from torch._inductor.metrics import get_metric_table, is_metric_table_enabled from torch.fx.experimental.symbolic_shapes import free_unbacked_symbols from torch.utils._sympy.symbol import free_symbol_is_type, SymT from torch.utils._triton import has_triton from . import comms, config, dependencies, ir, metrics from .codecache import write_text from .codegen.common import get_scheduling_for_device, Kernel from .comm_analysis import estimate_nccl_collective_runtime from .dependencies import Dep, MemoryDep, StarDep, WeakDep from .ir import ComputedBuffer, MultiOutput, MultiOutputLayout from .runtime.runtime_utils import green_text, red_text from .sizevars import SimplifyIndexing from .utils import ( cache_on_self, cmp, device_need_guard, get_device_tflops, get_dtype_size, get_gpu_dram_gbps, IndentedBuffer, is_collective, is_gpu, is_wait, sympy_product, ) from .virtualized import V log = logging.getLogger(__name__) fusion_log = torch._logging.getArtifactLogger(__name__, "fusion") class BaseSchedulerNode: group: Tuple[torch.device, Tuple[Tuple[sympy.Expr, ...], ...]] read_writes: dependencies.ReadWrites unmet_dependencies: Set[Dep] def __init__(self, scheduler: "Scheduler", node: ir.Buffer) -> None: self.scheduler: Scheduler = scheduler self.node: Optional[ir.Buffer] = node self.users: List[NodeUser] = [] self.inverse_users: List[BaseSchedulerNode] = [] self.node_users: List[BaseSchedulerNode] = [] self.set_read_writes(node.get_read_writes()) self.ancestors: Set[str] = set() self.min_order: int self.max_order: int self.last_usage: Set[ str ] = set() # buffers that won't be used after this kernel self.written = False def __repr__(self) -> str: return f"{type(self).__name__}(name={self.get_name()!r})" def debug_str(self) -> str: """Longer form printout for trace logs""" name = self.get_name() lines = [ f"{name}: {type(self).__name__}({type(getattr(self, 'node', None)).__name__})", f"{name}.writes = {pformat(self.read_writes.writes)}", f"{name}.unmet_dependencies = {pformat(self.unmet_dependencies)}", f"{name}.met_dependencies = {pformat(self.read_writes.reads - self.unmet_dependencies)}", f"{name}.users = {self.users}", ] try: lines += [ self.debug_str_extra(), ] except Exception: log.warning("Ignoring error in debug_str()", exc_info=True) return "\n".join(lines).rstrip() def debug_str_extra(self) -> str: return "" def log_details(self) -> None: log.info( "%s: unmet_dependencies = %s, writes = %s", self, self.unmet_dependencies, self.read_writes.writes, ) def update_mutated_names(self, renames: Dict[str, str]) -> None: self.set_read_writes(self.read_writes.rename(renames)) def add_fake_dep(self, dep: Dep) -> None: self.set_read_writes(self.read_writes.with_read(dep)) def set_users(self, users: List["NodeUser"]) -> None: # deduplicate result: Dict[int, NodeUser] = {} for use in users: if id(use.node) in result: result[id(use.node)] = use.merge(result[id(use.node)]) else: result[id(use.node)] = use self.users = list(result.values()) def set_last_usage( self, future_used_buffers: Set[str], mutation_real_name: Dict[str, str] ) -> None: used_buffers = self.used_or_aliased_buffer_names() used_buffers = {mutation_real_name.get(k, k) for k in used_buffers} self.last_usage = used_buffers - future_used_buffers def get_aliases(self) -> Sequence[str]: assert self.node is not None return self.node.get_inputs_that_alias_output() def get_mutations(self) -> List[str]: assert self.node is not None return self.node.get_mutation_names() def has_aliasing_or_mutation(self) -> bool: return bool(self.get_aliases() or self.get_mutations()) def set_read_writes(self, rw: dependencies.ReadWrites) -> None: self.read_writes = rw self.unmet_dependencies = self.read_writes.reads self.prune_deps() def op_counts(self) -> Counter[str]: return self.read_writes.op_counts def used_buffer_names(self) -> Set[str]: return { dep.name for dep in itertools.chain(self.read_writes.reads, self.read_writes.writes) } def used_or_aliased_buffer_names(self) -> Set[str]: used_names = set() deps = [ dep.name for dep in itertools.chain(self.read_writes.reads, self.read_writes.writes) ] while len(deps) > 0: dep = deps.pop() used_names.add(dep) if V.graph.name_to_buffer.get(dep): for alias in V.graph.name_to_buffer[dep].get_inputs_that_alias_output(): if alias not in used_names: deps.append(alias) return used_names def prune_deps(self) -> None: self.unmet_dependencies = { dep for dep in self.unmet_dependencies if dep.name not in self.scheduler.available_buffer_names } def prune_weak_deps(self) -> None: # Prune weak dependencies on buffers that have been removed def should_prune(dep: Dep) -> bool: return isinstance(dep, WeakDep) and dep.name in V.graph.removed_buffers to_remove = {dep for dep in self.read_writes.reads if should_prune(dep)} self.set_read_writes(self.read_writes.remove_reads(to_remove)) def prune_redundant_deps( self, name_to_fused_node: Dict[str, "BaseSchedulerNode"] ) -> None: _prune_redundant_deps(self, name_to_fused_node) def get_name(self) -> str: assert self.node is not None return self.node.get_name() def get_first_name(self) -> str: return self.get_name() def get_names(self) -> Set[str]: return {self.get_name()} def get_nodes(self) -> Sequence["BaseSchedulerNode"]: return [self] def get_device(self) -> torch.device: assert self.node is not None return self.node.get_device() def is_reduction(self) -> bool: return False def is_split_scan(self) -> bool: return False def is_template(self) -> bool: return False def is_extern(self) -> bool: return False def is_foreach(self) -> bool: return False def can_inplace(self, read_dep: dependencies.Dep) -> bool: return False def has_side_effects(self) -> bool: return False def decide_inplace_update(self) -> None: """ Decide if there should be inplace updates for the node and record the decision in the active kernel. """ assert self.node is not None if not self.node.should_allocate(): return if isinstance(self, (SchedulerNode,)) and ( self.node.get_inputs_that_alias_output() or self.node.get_mutation_names() ): return if ( isinstance(self, (SchedulerNode,)) and config.inplace_buffers and ( not isinstance(V.kernel, torch._inductor.codegen.simd.SIMDKernel) or getattr(V.kernel, "mutations", None) is not None ) ): from .codegen.wrapper import buffer_reuse_key ordered_reads = sorted(self.read_writes.reads, key=lambda x: x.name) for read in ordered_reads: input_node: Optional[ BaseSchedulerNode ] = self.scheduler.name_to_node.get(read.name) if ( input_node and V.graph.wrapper_code.can_reuse(input_node, self) and not isinstance(input_node, NopKernelSchedulerNode) ): assert input_node.users is not None remaining_uses = [ x for x in input_node.users if x.node.get_name() not in self.scheduler.available_buffer_names ] if ( len(remaining_uses) == 1 and remaining_uses[0].can_inplace and remaining_uses[0].node is self and input_node.node is not None and not isinstance( input_node.node.get_layout(), ( ir.MultiOutputLayout, ir.MutationLayoutSHOULDREMOVE, ), ) and not ( isinstance( input_node.node, (ir.FallbackKernel, ir.MultiOutput) ) and len(input_node.node.get_inputs_that_alias_output()) > 0 ) and buffer_reuse_key(input_node.node) == buffer_reuse_key(self.node) ): # hacky check for if V.kernel is a real kernel or NullHandler if hasattr(V.kernel, "args"): # if there isn't a triton kernel, then we don't need to call triton-specific things. # but TODO this might be a convenient place to signal to the Collective kernels to inplace # (and, can we make "kernel" less generic of a name?) V.kernel.args.make_inplace( input_node.get_name(), self.get_name() ) # mutations not tracked in cpp kernels if isinstance( V.kernel, torch._inductor.codegen.simd.SIMDKernel ): V.kernel.mutations.add(input_node.get_name()) V.kernel.mutations.add(self.get_name()) # update last usage of reused node self.last_usage.discard(input_node.get_name()) V.kernel.inplace_update_buffers[ self.get_name() ] = input_node.get_name() break def allocate(self) -> None: assert self.node is not None if not self.node.should_allocate(): return if isinstance(self, (SchedulerNode,)) and ( self.node.get_inputs_that_alias_output() or self.node.get_mutation_names() ): V.graph.wrapper_code.codegen_allocation(self.node) return # hacky check for if V.kernel is a real kernel or NullHandler if ( hasattr(V.kernel, "args") and self.get_name() in V.kernel.inplace_update_buffers ): V.graph.wrapper_code.codegen_inplace_reuse( self.scheduler.name_to_node[ V.kernel.inplace_update_buffers[self.get_name()] ].node, self.node, ) else: V.graph.wrapper_code.codegen_allocation(self.node) def can_free(self) -> bool: # There's no real allocated buffer, no need to free it assert self.node is not None if isinstance(self.node.layout, ir.NoneLayout): return False for use in self.users: if isinstance(use.node, OutputNode): return False return True def codegen_originating_info( self, buffer: IndentedBuffer, only_once: bool = True ) -> None: if not config.comment_origin: return if only_once and self.written: return assert self.node is not None origins = self.node.origins out_lines = [] for o in origins: if o.op == "output": # These are boring and samey continue out_lines.append("") # TODO(voz): Should the pragma be constant somewhere? out_lines.append("#pragma CMT ORIGIN:") op_info_str = f"#pragma CMT {o.op} {o.target}" if "seq_nr" in o.meta: op_info_str = op_info_str + f" seq_nr:{o.meta['seq_nr']}" out_lines.append(op_info_str) if "stack_trace" in o.meta: stack_trace = f"{o.meta['stack_trace']}" stack_trace_last_line = stack_trace.split("|")[-1] out_lines.append( "#pragma CMT " + stack_trace_last_line.replace("{", "{{") .replace("}", "}}") .replace("\n", "\\") ) out_lines.append("#pragma CMT END ORIGIN") out_lines.append("") if len(out_lines) == 0: return # TODO(voz): Ostensibly, we should not need this. But there are cases where C++ codegen does # not use BracesBuffer, so we have no good indicator of a C++ buffer atm. buffer.writelines(out_lines) self.written = True def get_read_write_buffers_sizes(self) -> int: """ Counting the number of bytes accessed for a kernel is surprisingly tricky. In particular, there is a differentiation between 'theoretical' memory accesses and practical memory accesses. For example, a layernorm kernel may actually access an input 3 times, but in theory, it only needs to access its input once (and may be optimized to do so through say, persistent reductions) Another example is that even though a buffer is passed in, we may not access the entire buffer. This may occur if we are accessing a slice of the buffer. Another tricky case is for indirect indexing, where the amount of bytes accessed depends on the values of the input. What this function aims to compute is the memory accesses for worst-case inputs, best-case optimization. What this means is that for each buffer we compute the amount of potential accesses in two ways and take the minimum. 1. Numel in ranges multiplied by number of deps the buffer has 2. The buffer size """ if isinstance(self, NopKernelSchedulerNode): return 0 if isinstance(self, ExternKernelSchedulerNode) and isinstance( self.node, MultiOutput ): # todo: Calculate this - it's kinda annoying. return 0 def try_size_hint(s: sympy.Expr) -> int: return V.graph.sizevars.size_hint(s, fallback=0) if isinstance(self, SchedulerNode): node_numel = try_size_hint( sympy_product(self.get_ranges()[0]) * sympy_product(self.get_ranges()[1]), ) else: node_numel = int(1e9) buf_accesses = collections.defaultdict(list) for dep in self.read_writes.reads | self.read_writes.writes: buf_accesses[dep.name].append(dep) reads = {dep.name for dep in self.read_writes.reads} writes = {dep.name for dep in self.read_writes.writes} def is_materialized(buf: str, snodes: Sequence[BaseSchedulerNode]) -> bool: users = [ user for user in self.scheduler.name_to_node[buf].users if not user.is_weak ] buf_uses = {user.node for user in users} return len(buf_uses - set(snodes)) > 0 if isinstance(self, FusedSchedulerNode): removed_buffers = { dep for dep in writes if not is_materialized(dep, self.snodes) } writes = writes - removed_buffers reads = reads - removed_buffers node_bytes = 0 for buf_name in reads | writes: buf_accessed_elems = sum(node_numel for dep in buf_accesses[buf_name]) buf: Union[ir.Buffer, ir.TensorBox] if buf_name in V.graph.name_to_buffer: buf = V.graph.name_to_buffer[buf_name] elif buf_name in V.graph.graph_inputs: buf = V.graph.graph_inputs[buf_name] else: continue def get_buf_elems(buf: Optional[Union[ir.Buffer, ir.TensorBox]]) -> int: if not buf: return 0 # Kind of a lazy way to get the MultiOutput nodes corresponding to # a MultiOutputLayout if isinstance(buf.layout, MultiOutputLayout): users = self.scheduler.name_to_node[buf.get_name()].users tot = 0 for user in users: assert isinstance(user.node, BaseSchedulerNode) if isinstance(user.node.node, MultiOutput): tot += get_buf_elems(user.node.node) else: # Buf is a MultiOutputLayout but not all of its # users are MultiOutputs... # TODO: Figure out what's going on return 0 return tot else: return try_size_hint(sympy_product(buf.get_size())) buf_elems = get_buf_elems(buf) node_bytes += min(buf_elems, buf_accessed_elems) * get_dtype_size( buf.get_dtype() ) return node_bytes def get_estimated_runtime(self) -> float: """ Returns estimated op runtime in nanoseconds (ns) """ layout = None dtype = None if not hasattr(self, "node") or not self.node: assert isinstance( self, (FusedSchedulerNode, ForeachKernelSchedulerNode) ), f"{type(self)=}" assert self.snodes if not self.snodes[0].node: return 0 layout = self.snodes[0].node.get_layout() dtype = self.snodes[0].node.get_dtype() else: layout = self.node.get_layout() dtype = self.node.get_dtype() if layout.device is not None and not is_gpu(layout.device.type): # default to no reordering based on runtime return 0 # Collective kernels if is_collective(self.node): assert self.node is not None try: return estimate_nccl_collective_runtime(self.node) except ValueError as e: # We don't know how to estimate runtime for this collective, # falling back to 0 log.info(e) return 0 elif is_wait(self.node): # ir.Wait is only used for collective ops. # The time needed for the collective op is already estimated and considered # when we are processing the collective op IR node, so ir.Wait takes 0 time # since it doesn't take extra time to get the result after the collective is completed. return 0 try: gpu_memory_bandwidth = get_gpu_dram_gbps() gpu_flops = get_device_tflops(dtype) * 10**12 except Exception: return 0 if isinstance(self, ExternKernelSchedulerNode): assert isinstance(self.node, ir.ExternKernel), f"{type(self.node)=}" op = kernel_name_to_op.get( getattr(self.node, "python_kernel_name", ""), None ) # if there is a resolved op, dry-run using fake mode and record flop count if op is not None: from torch._subclasses.fake_tensor import FakeTensorMode from torch.utils.flop_counter import FlopCounterMode if any( len(free_unbacked_symbols(n.get_numel())) > 0 for n in self.node.inputs ): # Tensor has unbacked symints, we don't know how to estimate # runtime for that today return 0 with FakeTensorMode() as fake_mode, FlopCounterMode( display=False ) as flop_counter_mode, V.set_current_node( self.node.fx_node ), V.set_fake_mode( fake_mode ): from .ir import ir_node_to_tensor fake_inputs = [ ir_node_to_tensor(input, guard_shape=False) for input in self.node.inputs ] cls = self.node.__class__ cls.process_kernel(op, *fake_inputs, **self.node.kwargs) # TODO(xmfan): find a better heuristic to model FLOPS/latency relationship factor = 1.0 counted_flops = flop_counter_mode.get_total_flops() counted_bytes = self.get_read_write_buffers_sizes() compute_time = (factor * counted_flops / gpu_flops) * 1e9 transfer_time = counted_bytes / gpu_memory_bandwidth # Return estimated runtime in nanoseconds return max(compute_time, transfer_time) elif isinstance(self, FusedSchedulerNode) or isinstance( self.node, ComputedBuffer ): # Return estimated runtime in nanoseconds (bytes / gbps) return self.get_read_write_buffers_sizes() / gpu_memory_bandwidth return 0 def get_template_node(self) -> Optional[ir.TemplateBuffer]: return None class WhyNoFuse: # TODO when we drop support for Python < 3.10, we can use # @dataclass(slots=True) instead of manually specifying __slots__. __slots__ = ["node1", "node2", "reason", "args"] reason: str args: Tuple[Any, ...] def __init__(self, node1: BaseSchedulerNode, node2: BaseSchedulerNode): self.node1 = node1 self.node2 = node2 def __call__(self, reason: str, *args: Any) -> None: self.reason = reason self.args = args fusion_log.debug(self) def __str__(self) -> str: return f"cannot fuse {self.node1.get_name()} with {self.node2.get_name()}: " + ( self.reason % self.args ) def pformat(obj: Any) -> str: if isinstance(obj, set): # pformat has trouble with sets of sympy exprs obj = sorted(obj, key=str) result = pprint.pformat(obj, indent=4) if "\n" in result: return f"\n{textwrap.indent(result, ' '*4)}" return result class OutputNode: def __init__(self, dep: StarDep) -> None: self.unmet_dependencies = {dep} self.inverse_users: List[BaseSchedulerNode] = [] def is_reduction(self) -> bool: return False def get_inputs_that_alias_output(self) -> Sequence[str]: return () def get_name(self) -> str: return "OUTPUT" __repr__ = get_name def _prune_redundant_deps( node: BaseSchedulerNode, name_to_fused_node: Dict[str, BaseSchedulerNode] ) -> None: """ Prunes weakdeps intended for mutation ordering on an upstream fused node if after fusion there is another dependency on the fused upstream node, making the weakdep redundant In essence this enforces an ordering on fusions. As fusions occur, weakdeps will be incrementally removed, enabling other fusions, ensuring they are fused in order. """ name_to_dep_count: Counter[str] = collections.Counter() for dep in node.unmet_dependencies: if not isinstance(dep, WeakDep): name_to_dep_count[name_to_fused_node[dep.name].get_name()] += 1 def should_prune(dep: Dep) -> bool: if isinstance(dep, WeakDep): is_redundant = ( name_to_dep_count[name_to_fused_node[dep.name].get_name()] > 0 ) # These can occur because fused nodes always gather deps from their snodes # If B has a weakdep on A # B gets fused with C, then any time BC is fused, the weakdep will reappear is_self_dep = name_to_fused_node[dep.name] == node return is_redundant or is_self_dep else: return False deps_to_prune = {dep for dep in node.unmet_dependencies if should_prune(dep)} if deps_to_prune: node.unmet_dependencies = node.unmet_dependencies - deps_to_prune node.set_read_writes(node.read_writes.remove_reads(deps_to_prune)) # TODO(xmfan): reuse an existing mapping for this if it exists, or formalize this into ir.py:ExternKernel kernel_name_to_op = { "extern_kernels.convolution": torch.ops.aten.convolution, "extern_kernels.mm": torch.ops.aten.mm, "extern_kernels.bmm": torch.ops.aten.bmm, "extern_kernels.addmm": torch.ops.aten.addmm, } class ExternKernelSchedulerNode(BaseSchedulerNode): def debug_str_extra(self) -> str: return f"{self.get_name()}.node.kernel = {getattr(self.node, 'python_kernel_name', None)}" def is_extern(self) -> bool: return True def has_side_effects(self) -> bool: assert self.node is not None return hasattr(self.node, "has_side_effects") and self.node.has_side_effects() class NopKernelSchedulerNode(BaseSchedulerNode): pass class SchedulerNode(BaseSchedulerNode): def __init__( self, scheduler: "Scheduler", node: Union[ir.ComputedBuffer, ir.TemplateBuffer], ) -> None: super().__init__(scheduler, node) self._compute_attrs() def _compute_attrs( self, extra_indexing_constraints: Optional[Tuple[Dict[Any, Any], List[Any]]] = None, ) -> None: assert isinstance(self.node, (ir.ComputedBuffer, ir.TemplateBuffer)) self._sizes, self._body = self.node.simplify_and_reorder( extra_indexing_constraints=extra_indexing_constraints ) group_fn = self.scheduler.get_backend(self.node.get_device()).group_fn self.group = (self.node.get_device(), group_fn(self._sizes)) if isinstance(self.node, ir.TemplateBuffer): self.set_read_writes(self.node.normalized_read_writes()) else: self.set_read_writes( dependencies.extract_read_writes( self._body, *self._sizes, normalize=True ) ) def recompute_size_and_body( self, extra_indexing_constraints: Tuple[Dict[Any, Any], List[Any]] ) -> None: self._compute_attrs(extra_indexing_constraints=extra_indexing_constraints) def debug_str_extra(self) -> str: name = self.get_name() lines = [ f"{name}.group.device = {self.group[0]}", f"{name}.group.iteration = {self.group[1]}", f"{name}.sizes = {self._sizes}", ] for dep in self.read_writes.reads_and_writes(): buf_name = dep.name buf = V.graph.get_buffer(buf_name) lines.append(f"{buf_name}_layout = {pformat(buf.layout)}") if self.get_aliases(): lines.append(f"{name}.aliases = {pformat(self.get_aliases())}") if self.get_mutations(): lines.append(f"{name}.mutations = {pformat(self.get_mutations())}") if isinstance(self._body, ir.LoopBody): lines.append(f"class {name}_loop_body:") lines.append(textwrap.indent(self._body.debug_str(), " ")) assert self.node is not None if ir.is_triton(self.node.get_device()): lines.extend(debug_triton_code(self)) return "\n".join(lines) def get_ranges(self) -> Sequence[Sequence[sympy.Expr]]: return self._sizes def is_reduction(self) -> bool: assert isinstance( self.node, (ir.ComputedBuffer, ir.TemplateBuffer) ), f"{type(self.node)=}" return bool(self.node.get_reduction_type()) def is_split_scan(self) -> bool: assert isinstance( self.node, (ir.ComputedBuffer, ir.TemplateBuffer) ), f"{type(self.node)=}" return isinstance(self.node, ir.ComputedBuffer) and isinstance( self.node.data, ir.SplitScan ) def is_template(self) -> bool: return isinstance(self.node, ir.TemplateBuffer) def get_template_node(self) -> Optional[ir.TemplateBuffer]: return self.node if isinstance(self.node, ir.TemplateBuffer) else None def run(self, *index_vars: Sequence[sympy.Expr]) -> None: self.decide_inplace_update() self.mark_run() self.codegen(index_vars) def mark_run(self) -> None: self.allocate() def ranges_from_index_vars( self, index_vars: Sequence[Sequence[sympy.Expr]] ) -> Dict[sympy.Expr, sympy.Expr]: sizes = self._sizes assert sum(map(len, sizes)) == sum(map(len, index_vars)) var_ranges = dict( zip( itertools.chain.from_iterable(index_vars), itertools.chain.from_iterable(sizes), ) ) return var_ranges def codegen(self, index_vars: Sequence[Sequence[sympy.Expr]]) -> None: var_ranges = self.ranges_from_index_vars(index_vars) try: with V.set_ops_handler( SimplifyIndexing(V.get_ops_handler(), var_ranges) ), V.kernel.set_current_node(self): self._body(*index_vars) except Exception: log.fatal("Error in codegen for %s", self.node) raise def pointwise_read_writes(self) -> dependencies.ReadWrites: """ Get the memory dependencies in the non-reduction axis. """ sizes, reduction_sizes = self._sizes def fn(index: Sequence[sympy.Symbol]) -> str: return self._body(index, [sympy.Integer(0) for _ in reduction_sizes]) return dependencies.extract_read_writes(fn, sizes) def can_inplace(self, read_dep: dependencies.Dep) -> bool: if self.get_aliases() or self.is_template(): return False if len(self.read_writes.writes) == 1 and isinstance( read_dep, dependencies.MemoryDep ): write_dep = next(iter(self.read_writes.writes)) assert isinstance(write_dep, dependencies.MemoryDep), f"{type(write_dep)=}" return read_dep.index == write_dep.index and read_dep.size == write_dep.size return False @cache_on_self def _get_atomic_add_buffers(self) -> Set[str]: buffers_store_as_atomic_add = set() if isinstance(self._body, ir.LoopBody): for node in self._body.get_nodes(): if ( node.op == "call_method" and node.target == "store" and ( ("mode" in node.kwargs and node.kwargs["mode"] == "atomic_add") or (len(node.args) == 5 and node.args[4] == "atomic_add") ) ): buffers_store_as_atomic_add.add( node.kwargs["name"] if "name" in node.kwargs else (node.args[1] if len(node.args) >= 2 else "") ) return buffers_store_as_atomic_add class FusedSchedulerNode(BaseSchedulerNode): """ This is a "fake" scheduler node that represents a group of scheduler nodes that are meant to be fused together. The way it does this is by maintaining its unmet dependencies as the union of its constituent nodes. """ @classmethod def fuse( cls, node1: BaseSchedulerNode, node2: BaseSchedulerNode ) -> "FusedSchedulerNode": assert node1.scheduler is node2.scheduler assert isinstance(node1, (SchedulerNode, FusedSchedulerNode)) assert isinstance(node2, (SchedulerNode, FusedSchedulerNode)) nodes = list(itertools.chain(node1.get_nodes(), node2.get_nodes())) return cls(node1.scheduler, nodes) def __init__( self, scheduler: "Scheduler", snodes: Sequence[BaseSchedulerNode] ) -> None: # NB: No need to call super().__init__() because we don't need to re-use any of its logic. self.snodes = snodes self.scheduler = scheduler self.node = None self.users: List[NodeUser] = [] self.inverse_users = [] self.node_users = [] self.group = max(snodes, key=lambda x: int(x.is_reduction())).group self.ancestors = set.union( *[x.ancestors for x in snodes if x.ancestors is not None] ) self.set_read_writes( dependencies.ReadWrites.merge_list([x.read_writes for x in snodes]) ) self.unmet_dependencies = { dep for dep in set.union(*[x.unmet_dependencies for x in snodes]) if dep.name not in self.get_names() } - self.read_writes.writes self.min_order = min(x.min_order for x in self.snodes) self.max_order = max(x.max_order for x in self.snodes) @cache_on_self def get_name(self) -> str: return "_".join([x.get_name() for x in self.snodes]) def get_first_name(self) -> str: return self.snodes[0].get_name() @cache_on_self def get_names(self) -> Set[str]: return set.union(*[x.get_names() for x in self.snodes]) def debug_str_extra(self) -> str: lines = [ f"{self.get_name()}.snodes[{i}] =\n{node.debug_str()}" for i, node in enumerate(self.snodes) ] node = self.snodes[0].node assert node is not None device = node.get_device() if ir.is_triton(device): lines.extend(debug_triton_code(self)) return textwrap.indent("\n".join(lines).rstrip(), " ") def set_last_usage( self, future_used_buffers: Set[str], mutation_real_name: Dict[str, str] ) -> None: # Set self.last_usage using the global information # This will be used for inter-kernel optimisations super().set_last_usage(future_used_buffers, mutation_real_name) # Set self.last_usage on the snodes # This will be used for optimisations within the kernel future_used_buffers: Set[str] = set() for node in reversed(self.snodes): node.set_last_usage(future_used_buffers, mutation_real_name) future_used_buffers.update(node.last_usage) @cache_on_self def used_buffer_names(self) -> Set[str]: return set.union(*[x.used_buffer_names() for x in self.snodes]) @cache_on_self def used_or_aliased_buffer_names(self) -> Set[str]: return set.union(*[x.used_or_aliased_buffer_names() for x in self.snodes]) def get_nodes(self) -> Sequence[BaseSchedulerNode]: return self.snodes def __repr__(self) -> str: return f"{type(self).__name__}(nodes={self.get_name()})" @cache_on_self def is_reduction(self) -> bool: return any(x.is_reduction() for x in self.snodes) @cache_on_self def is_split_scan(self) -> bool: return any(x.is_split_scan() for x in self.snodes) @cache_on_self def is_template(self) -> bool: return any(x.is_template() for x in self.snodes) @cache_on_self def get_template_node(self) -> Optional[ir.TemplateBuffer]: for node in self.snodes: if node.is_template(): return node.get_template_node() return None def get_device(self) -> torch.device: return self.group[0] @cache_on_self def has_aliasing_or_mutation(self) -> bool: return any(x.has_aliasing_or_mutation() for x in self.snodes) @cache_on_self def op_counts(self) -> Counter[str]: op_counts: Counter[str] = collections.Counter() for node in self.snodes: op_counts.update(node.op_counts()) return op_counts # None of these need to be implemented, as a FusedSchedulerNode is just an # abstraction for scheduling purposes def update_mutated_names(self, renames: Dict[str, str]) -> None: raise NotImplementedError def add_fake_dep(self, name: Dep) -> None: raise NotImplementedError def set_users(self, users: List["NodeUser"]) -> None: raise NotImplementedError def get_aliases(self) -> Sequence[str]: raise NotImplementedError def get_mutations(self) -> List[str]: raise NotImplementedError def can_inplace(self, read_dep: dependencies.Dep) -> bool: raise NotImplementedError def allocate(self) -> None: raise NotImplementedError def can_free(self) -> bool: raise NotImplementedError def debug_str(self) -> str: """Longer form printout for trace logs""" name = self.get_name() node_typestr = ",".join(type(n).__name__ for n in self.snodes) lines = [ f"{name}: {type(self).__name__}({node_typestr})", f"{name}.writes = {pformat(self.read_writes.writes)}", f"{name}.unmet_dependencies = {pformat(self.unmet_dependencies)}", f"{name}.met_dependencies = {pformat(self.read_writes.reads - self.unmet_dependencies)}", f"{name}.users = {self.users}", ] try: lines += [ self.debug_str_extra(), ] except Exception: log.warning("Ignoring error in debug_str()", exc_info=True) return "\n".join(lines).rstrip() class ForeachKernelSchedulerNode(FusedSchedulerNode): """Scheduler node which consists of a list of scheduler nodes that each operate on a distinct tensor in a list of tensors.""" def get_consumer_subnode_for( self, producer: BaseSchedulerNode ) -> Optional[BaseSchedulerNode]: if producer.get_name() in self.read_to_node: return self.read_to_node[producer.get_name()] return None def get_producer_subnode_for( self, consumer: BaseSchedulerNode ) -> Optional[BaseSchedulerNode]: for rd in consumer.read_writes.reads: if rd.name in self.name_to_node: return self.name_to_node[rd.name] return None @classmethod def can_fuse(cls, producer: BaseSchedulerNode, consumer: BaseSchedulerNode) -> bool: why = WhyNoFuse(producer, consumer) if producer.is_foreach() and consumer.is_foreach(): producer = typing.cast(ForeachKernelSchedulerNode, producer) consumer = typing.cast(ForeachKernelSchedulerNode, consumer) foreach_match = len(producer.snodes) == len(consumer.snodes) if not foreach_match: why("foreach do not have same length") return foreach_match and all( producer.scheduler.can_fuse(l, r) for l, r in zip(producer.snodes, consumer.snodes) ) elif consumer.is_foreach(): if producer.is_reduction(): why( "candidate producer is a reduction, foreach ops cannot be fused with reductions currently" ) return False consumer = typing.cast(ForeachKernelSchedulerNode, consumer) consumer_subnode = consumer.get_consumer_subnode_for(producer) if consumer_subnode is not None: return consumer.scheduler.can_fuse(producer, consumer_subnode) why("candidate producer is not dep of any foreach consumer") return False elif producer.is_foreach(): if consumer.is_reduction(): why( "candidate consumer is a reduction, foreach ops cannot be fused with reductions currently" ) return False producer = typing.cast(ForeachKernelSchedulerNode, producer) producer_subnode = producer.get_producer_subnode_for(consumer) if producer_subnode is not None: return producer.scheduler.can_fuse(producer_subnode, consumer) why("candidate consumer has no dep in any foreach producer") return False raise AssertionError( "At least one node passed to ForeachKernelSchedulerNode.can_fuse should be a foreach node" ) @classmethod def fuse( cls, producer: BaseSchedulerNode, consumer: BaseSchedulerNode ) -> "ForeachKernelSchedulerNode": assert producer.is_foreach() or consumer.is_foreach() prev_node_1 = None prev_node_2 = None fused_nodes: List[BaseSchedulerNode] if producer.is_foreach() and consumer.is_foreach(): producer = typing.cast(ForeachKernelSchedulerNode, producer) consumer = typing.cast(ForeachKernelSchedulerNode, consumer) fused_nodes = [ FusedSchedulerNode.fuse(l, r) for l, r in zip(producer.snodes, consumer.snodes) ] elif producer.is_foreach(): producer = typing.cast(ForeachKernelSchedulerNode, producer) producer_subnode = producer.get_producer_subnode_for(consumer) fused_nodes = [] prev_node_1 = producer prev_node_2 = None for node in producer.snodes: if node is producer_subnode: new_node = FusedSchedulerNode.fuse(node, consumer) prev_node_2 = new_node fused_nodes.append(new_node) else: fused_nodes.append(node) elif consumer.is_foreach(): consumer = typing.cast(ForeachKernelSchedulerNode, consumer) consumer_subnode = consumer.get_consumer_subnode_for(producer) fused_nodes = [] prev_node_1 = consumer prev_node_2 = None for node in consumer.snodes: if node is consumer_subnode: new_node = FusedSchedulerNode.fuse(producer, node) prev_node_2 = new_node fused_nodes.append(new_node) else: fused_nodes.append(node) return cls(producer.scheduler, fused_nodes, prev_node_1, prev_node_2) def __init__( self, scheduler: "Scheduler", nodes: Sequence[BaseSchedulerNode], prev_node_1: Optional[BaseSchedulerNode] = None, prev_node_2: Optional[BaseSchedulerNode] = None, ) -> None: self.read_to_node = {} self.name_to_node = {} if prev_node_1 is None or prev_node_2 is None: super().__init__(scheduler, nodes) for node in nodes: for read in node.read_writes.reads: self.read_to_node[read.name] = node for name in node.get_names(): self.name_to_node[name] = node else: self.scheduler = scheduler self.snodes = nodes self.node = None self.users: List[NodeUser] = [] self.set_read_writes( dependencies.ReadWrites.merge_list( [prev_node_1.read_writes, prev_node_2.read_writes] ) ) self.unmet_dependencies = { dep for dep in set.union( prev_node_1.unmet_dependencies, prev_node_2.unmet_dependencies ) if dep.name not in self.get_names() } - self.read_writes.writes self.min_order = min([prev_node_1.min_order, prev_node_2.min_order]) self.max_order = max([prev_node_1.max_order, prev_node_2.max_order]) if prev_node_1.is_foreach(): assert isinstance(prev_node_1, ForeachKernelSchedulerNode) foreach_node, other_node = prev_node_1, prev_node_2 else: assert isinstance(prev_node_2, ForeachKernelSchedulerNode) foreach_node, other_node = prev_node_2, prev_node_1 self.ancestors = foreach_node.ancestors self.ancestors.update(other_node.ancestors) self.name_to_node = foreach_node.name_to_node for name in other_node.get_names(): self.name_to_node[name] = other_node self.group = (nodes[0].get_device(), ((sympy.Expr("foreach"),),)) self.origins: Set[torch.fx.Node] = set() def mark_run(self) -> None: raise NotImplementedError def codegen(self) -> None: assert isinstance(self.node, ir.ComputedBuffer), f"{type(self.node)=}" self.node.get_store_function()(self.node.make_loader()()) def can_free(self) -> bool: raise NotImplementedError def is_foreach(self) -> bool: return True def get_subkernel_nodes(self) -> List[BaseSchedulerNode]: """Returns a list of nodes which comprise the foreach kernel, operating on corresponding elements of our input lists. These nodes may be vertically fused.""" return list(self.snodes) def get_nodes(self) -> Sequence[BaseSchedulerNode]: """Returns all nodes contained in this kernel, unpacking fused nodes into their constituent scheduler nodes.""" return list(itertools.chain.from_iterable(x.get_nodes() for x in self.snodes)) def get_first_name(self) -> str: return self.snodes[0].get_first_name() def prune_redundant_deps( self, name_to_fused_node: Dict[str, BaseSchedulerNode] ) -> None: _prune_redundant_deps(self, name_to_fused_node) for node in self.snodes: node.prune_redundant_deps(name_to_fused_node) def pick_loop_order( stride_lengths: List[List[int]], sizes: List[sympy.Expr], priority_idx: Tuple[int, ...] = (), ) -> List[int]: """ A heuristic to decide loop iteration orders. This has not been well tuned and may be something we should autotune. """ @functools.cmp_to_key def index_cmp(a: int, b: int) -> int: if sizes[a] == 1 or sizes[b] == 1: # 1-sizes don't matter, just move them to the end return cmp(sizes[a] == 1, sizes[b] == 1) # Take abs, otherwise flipped dimensions are treated as smaller # strides than contiguous dims stride_len_a = [abs(sl[a]) for sl in stride_lengths] stride_len_b = [abs(sl[b]) for sl in stride_lengths] # equivalent to # np.logical_or(stride_lengths[:, b] == 0, stride_lengths[:, a] < stride_lengths[:, b]).all() a_first = sum( sl_b == 0 or sl_a < sl_b for sl_a, sl_b in zip(stride_len_a, stride_len_b) ) b_first = sum( sl_a == 0 or sl_b < sl_a for sl_a, sl_b in zip(stride_len_a, stride_len_b) ) if a_first > b_first: return -1 if b_first > a_first: return 1 # otherwise contiguous return cmp(b, a) order = list(reversed(range(len(stride_lengths[0])))) if len(priority_idx) > 0: # if we have priority node, only use that node's order stride_lengths = [stride_lengths[pi] for pi in priority_idx] if config.pick_loop_orders: order.sort(key=index_cmp) return order @dataclasses.dataclass class NodeUser: node: Union[BaseSchedulerNode, OutputNode] can_inplace: bool = False # A weak user must be scheduled after a given node, but doesn't actually # use the result is_weak: bool = False def __hash__(self) -> int: return hash((self.node.get_name(), self.can_inplace, self.is_weak)) def __eq__(self, other: object) -> bool: return ( isinstance(other, NodeUser) and self.get_name() == other.get_name() and self.can_inplace == other.can_inplace and self.is_weak == other.is_weak ) def get_name(self) -> str: return self.node.get_name() def merge(self, other: "NodeUser") -> "NodeUser": assert self.node is other.node return NodeUser( self.node, self.can_inplace and other.can_inplace, self.is_weak and other.is_weak, ) _post_grad_graph_counter = itertools.count() class Scheduler: __dep_size_hint_cache: Dict[Dep, int] @dynamo_timed def __init__(self, nodes: List[ir.Buffer]) -> None: super().__init__() self.__dep_size_hint_cache = {} V.graph.scheduler = self self.backends: Dict[torch.device, BaseScheduling] = {} self.post_grad_graph_id = next(_post_grad_graph_counter) self.available_buffer_names = { *V.graph.graph_inputs.keys(), *V.graph.constants.keys(), *V.graph.torchbind_constants.keys(), } self.nodes = [self.create_scheduler_node(n) for n in nodes] # some new constants could have been created above self.available_buffer_names.update(V.graph.constants.keys()) for node in self.nodes: node.prune_deps() self.name_to_node: Dict[str, BaseSchedulerNode] = { n.get_name(): n for n in self.nodes } self.name_to_fused_node: Dict[ str, BaseSchedulerNode ] = dict() # set in fuse_nodes() # mutation_real_name: Maps back to the original name for codegen # Example: # If you mutate buf0 inside of buf1's kernel, then: # mutation_real_name = {"buf0" : "buf1"} # all subsequent uses of buf0 become buf1's usage in dependency graph self.mutation_real_name: Dict[str, str] = {} # We handle mutation by renaming modified versions of the same # buffer in the dependency graph to prevent cycles. # mutation_renames: tracks the current name for a given buffer # (changed once per mutation) # Example: # If you mutate buf0 inside of buf1's kernel, then: # mutation_renames = {"buf1" : "buf0"} # in codegen we only use buf0, never buf1 self.mutation_renames: Dict[str, str] = {} self.compute_dependencies() self.topological_sort_schedule() self.dead_node_elimination() if config.reorder_for_compute_comm_overlap: comms.decide_global_ordering_of_comms(self.nodes) self.compute_ancestors() metrics.ir_nodes_pre_fusion += len(self.nodes) V.debug.ir_pre_fusion(self.nodes) self.num_orig_nodes = len(self.nodes) self.name_to_fused_node = {n.get_name(): n for n in self.nodes} self.create_foreach_nodes() self.topological_sort_schedule() self.logged_slow_fusion: Set[Tuple[str, str]] = set() self.fuse_nodes() self.finalize_multi_template_buffers() if config.reorder_for_compute_comm_overlap: # Refresh node_users and inverse_users to reflect fused nodes self.compute_node_users() self.nodes = comms.reorder_compute_and_comm_for_overlap(self.nodes) self.compute_last_usage() V.debug.ir_post_fusion(self.nodes) V.debug.graph_diagram(self.nodes) self.debug_draw_graph() # used during codegen: self.current_device: Optional[torch.device] = None self.buffer_names_to_free: Set[str] = set() # fx graph node to the position it appears in the graph # for debug attribution self.origin_to_index: Dict[torch.fx.Node, int] = {} get_metric_table("graph_stats").add_row( lambda: { "graph_id": self.post_grad_graph_id, "num_nodes_before_fusion": self.num_orig_nodes, "num_nodes_after_fusion": len(self.nodes), } ) def get_current_device_or_throw(self) -> torch.device: if device := self.current_device: return device else: raise RuntimeError("No current device") def debug_draw_graph(self) -> None: """Generate an image of the graph for debugging""" if os.environ.get("INDUCTOR_WRITE_SCHEDULER_GRAPH", None) == "1": from .debug import draw_buffers draw_buffers(self.nodes, print_graph=True) def debug_print_nodes(self, label: str) -> None: if log.isEnabledFor(logging.INFO): log.info("%s:", label) for node in self.nodes: node.log_details() def create_scheduler_node(self, node: ir.Buffer) -> BaseSchedulerNode: assert ( node.origins is not None ), "All nodes passed to scheduling must have an origin" if node.is_no_op(): return NopKernelSchedulerNode(self, node) elif isinstance(node, (ir.ComputedBuffer, ir.TemplateBuffer)): return SchedulerNode(self, node) elif isinstance(node, ir.ExternKernel): return ExternKernelSchedulerNode(self, node) else: raise NotImplementedError(node) def create_foreach_nodes(self) -> None: removed_node_names = set() fe_nodes = [] kept_node_names = self.name_to_fused_node.keys() for names in V.graph.lists.values(): names = [ name for name in names if name in kept_node_names and not isinstance(self.name_to_node[name], NopKernelSchedulerNode) ] if not names: # All nodes eliminated continue removed_node_names.update(names) snodes = [self.name_to_node[name] for name in names] fe_node = ForeachKernelSchedulerNode(self, snodes) fe_nodes.append(fe_node) for name in names: self.name_to_fused_node[name] = fe_node self.nodes = [ node for node in self.nodes if node.get_name() not in removed_node_names ] + list(fe_nodes) def compute_dependencies(self) -> None: """ Create dependency edges between nodes, handling aliasing and mutation properly. """ T = TypeVar("T") class DedupList(Generic[T]): """ This data structure behaves like a list except it makes sure the elements remain unique. Normally one could use a set/dict for this purpose however the list in question gets elements appended as it is being iterated over which means that we need to keep the list semantics. """ def __init__( self, items: Optional[List[T]] = None, membership: Optional[Set[T]] = None, ) -> None: self.items = items or list() self.membership = membership or set() def append(self, node_user: T) -> None: if node_user in self.membership: return self.items.append(node_user) self.membership.add(node_user) def __add__(self, other: "DedupList[T]") -> "DedupList[T]": new_membership = set.union(self.membership, other.membership) new_items = self.items + [ x for x in other.items if x not in self.membership ] return DedupList(new_items, new_membership) name_to_users: DefaultDict[str, DedupList[NodeUser]] = collections.defaultdict( DedupList ) # handle aliasing by using python aliasing in name_to_users # if foo aliases bar then we will make name_to_users["foo"] point # to the same python list as name_to_users["bar"] for node1 in self.nodes: node1_name = node1.get_name() for node2_name in node1.get_aliases(): if node1_name in name_to_users and node2_name in name_to_users: # merge the two list1 = name_to_users[node1_name] list2 = name_to_users[node2_name] combined = list1 + list2 for key in name_to_users.keys(): if name_to_users[key] is list1 or name_to_users[key] is list2: name_to_users[key] = combined elif node1_name in name_to_users: name_to_users[node2_name] = name_to_users[node1_name] else: name_to_users[node1_name] = name_to_users[node2_name] def rename(n: str) -> str: if n in self.mutation_renames: return rename(self.mutation_renames[n]) return n def dep_closure(node_name: str) -> Set[str]: reachable_names = {node_name} node = self.name_to_node[node_name] write_dep = next(iter(node.read_writes.writes)) for read_dep in node.read_writes.reads: if ( read_dep.name in self.name_to_node and isinstance(read_dep, dependencies.MemoryDep) and isinstance(write_dep, dependencies.MemoryDep) and read_dep.index == write_dep.index and read_dep.size == write_dep.size ): reachable_names.update(dep_closure(read_dep.name)) return reachable_names def add_user( used_by_name: str, user_node: Union[BaseSchedulerNode, OutputNode], can_inplace: bool = False, is_weak: bool = False, ) -> None: name_to_users[rename(used_by_name)].append( NodeUser(user_node, can_inplace, is_weak) ) unbacked_symbol_to_origin_node = {} # NB: None means that the dependency is on an input. Don't actually # generate a dependency because if we do, Inductor will start trying # to free the unbacked int but that's pointless for name, val in V.graph.graph_inputs.items(): if isinstance(val, sympy.Expr): for fs in val.free_symbols: unbacked_symbol_to_origin_node[fs] = None for node in self.nodes: log.debug("scheduling %s", node.node) # unbacked symbols don't follow ordinary buffer dependencies, so # we track their def/uses separately assert node.node is not None unbacked_symbol_defs = sorted( node.node.get_unbacked_symbol_defs(), key=lambda x: x.name ) for s in unbacked_symbol_defs: assert isinstance(s, sympy.Symbol) # Pick the first definer as canonical. There may be multiple # because if a MultiOutputLayout buffer propagates an unbacked # symint to multiple outputs, they will all claim to def it. if s not in unbacked_symbol_to_origin_node: unbacked_symbol_to_origin_node[s] = node.get_name() unbacked_symbol_uses = sorted( node.node.get_unbacked_symbol_uses(), key=lambda x: x.name ) # if a kernel takes unbacked symints, register dependencies for s in unbacked_symbol_uses: assert ( s in unbacked_symbol_to_origin_node ), f"{s} not in {unbacked_symbol_to_origin_node}" if (r := unbacked_symbol_to_origin_node[s]) is not None: node.add_fake_dep(StarDep(r)) if ( len(node.read_writes.writes) == 1 and (dep := next(iter(node.read_writes.writes))) and isinstance(dep, MemoryDep) ): node_mode = dep.mode else: node_mode = None # a node will mutate either 0 or 1 buffers assert len(node.get_mutations()) <= 1 for alt_name in node.get_mutations(): alt_name = rename(alt_name) # this node must run after the prior writer add_user(alt_name, node) node.add_fake_dep(StarDep(alt_name, mode=node_mode)) for other_node in name_to_users[alt_name].items: # this node must run after all prior readers other_name = rename(other_node.get_name()) known_dep_node_names = dep_closure(node.get_name()) if other_name not in known_dep_node_names: # If this node already directly or indirectly depends on other_node, # we don't need to insert an extra dep. node.add_fake_dep(WeakDep(other_name)) add_user(other_name, node, is_weak=True) # add normal non-mutation dependencies for read in node.read_writes.reads: is_weak = isinstance(read, WeakDep) add_user(read.name, node, node.can_inplace(read), is_weak) node.update_mutated_names(self.mutation_renames) # update our renaming scheme for the next iteration for alt_name in node.get_mutations(): self.mutation_renames[rename(alt_name)] = node.get_name() self.mutation_renames[alt_name] = node.get_name() self.mutation_real_name[node.get_name()] = self.mutation_real_name.get( alt_name, alt_name ) # make sure outputs aren't dead-code-eliminated for node_name in V.graph.get_output_names(): log.debug("scheduling output %s", node_name) add_user(node_name, OutputNode(StarDep(node_name))) # make sure unbacked symints aren't dead-code-eliminated for node in V.graph.graph_outputs: for s in node.get_unbacked_symbol_uses(): assert ( s in unbacked_symbol_to_origin_node ), f"{s} not in {unbacked_symbol_to_origin_node.keys()}" if (node_name := unbacked_symbol_to_origin_node[s]) is not None: log.debug( "scheduling output %s for unbacked symint %s", node_name, s ) add_user(node_name, OutputNode(StarDep(node_name))) # make sure input mutation isn't dead-code-eliminated for name in self.mutation_renames: if name in V.graph.graph_inputs: add_user(name, OutputNode(StarDep(name))) V.graph.mutated_inputs.add(name) elif name in V.graph.constants: # In AOTI, module parameters and buffers are not lifted as graph inputs add_user(name, OutputNode(StarDep(name))) inp_names = { name: index for index, name in enumerate(V.graph.graph_inputs.keys()) } V.graph.mutated_input_idxs = [ inp_names[name] for name in V.graph.mutated_inputs ] # copy users information onto the nodes for node in self.nodes: node.set_users(name_to_users[node.get_name()].items) # populate inverse_users for node in self.nodes: for user in node.users: user.node.inverse_users.append(node) def compute_node_users(self) -> None: # set up buffer name to (fused)snode mapping buf_to_snode: Dict[str, BaseSchedulerNode] = {} for node in self.nodes: if isinstance(node, FusedSchedulerNode): for x in node.snodes: buf_to_snode[x.get_name()] = node buf_to_snode[node.get_name()] = node for node in self.nodes: node.node_users = [] node.inverse_users = [] # compute inverse_users for node in self.nodes: inverse_users: List[BaseSchedulerNode] = [] for dep in node.unmet_dependencies: assert dep.name in buf_to_snode dep_node = buf_to_snode[dep.name] inverse_users.append(dep_node) node.inverse_users = inverse_users # compute node_users # TODO: ideally, we should deduplicate .users and .node_users, # but currently .users contains extra information that's difficult to # extract into a standalone container. node_to_users: Dict[BaseSchedulerNode, List[BaseSchedulerNode]] = {} for node in self.nodes: for inverse_user in node.inverse_users: node_to_users.setdefault(inverse_user, []).append(node) for node, users in node_to_users.items(): node.node_users = users def dead_node_elimination(self) -> None: """ Remove any nodes without users """ again = True # repeat until a fixed point while again: updated_nodes = [] for node in self.nodes: def can_eliminate_user(user: NodeUser) -> bool: return user.is_weak or user.get_name() in V.graph.removed_buffers can_eliminate = not node.has_side_effects() and all( can_eliminate_user(u) for u in node.users ) if not can_eliminate: updated_nodes.append(node) else: # dead code log.debug("removed dead node: %s", node.get_name()) V.graph.removed_buffers.add(node.get_name()) again = len(self.nodes) > len(updated_nodes) self.nodes = updated_nodes # Prune any WeakDeps no longer needed for node in self.nodes: node.prune_weak_deps() def topological_sort_schedule(self) -> None: """ Ensure self.nodes is in topologically sorted order """ seen: Set[BaseSchedulerNode] = set() name_to_node: Dict[str, BaseSchedulerNode] = dict() result: List[BaseSchedulerNode] = [] def visit(n: BaseSchedulerNode) -> None: if n not in seen: seen.add(n) for dep in sorted(n.unmet_dependencies, key=lambda d: d.name): visit(name_to_node[dep.name]) result.append(n) for node in self.nodes: for name in node.get_names(): name_to_node[name] = node for node in self.nodes: visit(node) self.nodes = result def compute_ancestors(self) -> None: """ Populate each node.ancestors """ # note self.nodes is topologically sorted name_to_ancestors: Dict[str, Set[str]] = {} for node in self.nodes: ancestors = set() for dep in node.unmet_dependencies: ancestors.add(dep.name) ancestors |= name_to_ancestors[dep.name] name_to_ancestors[node.get_name()] = ancestors node.ancestors = ancestors for order, node in enumerate(self.nodes): node.min_order = order node.max_order = order def fuse_nodes(self) -> None: """ Mutates self.nodes to combine nodes into FusedSchedulerNodes. """ for i in range(10): old_len = len(self.nodes) fusion_log.debug( "===== attempting fusion (%d/10): %d nodes =====", i + 1, old_len, ) self.fuse_nodes_once() new_len = len(self.nodes) fusion_log.debug( "completed fusion round (%d/10): fused %d nodes into %d nodes\n", i + 1, old_len, new_len, ) if new_len == old_len or new_len == 1: fusion_log.debug("===== fusion complete (%d iterations) =====", i + 1) break def benchmark_fused_nodes( self, nodes: Sequence[BaseSchedulerNode] ) -> Tuple[float, str]: """ Benchmark fused list of nodes and return the execution time in milliseconds on randomly generated inputs. """ assert len(nodes) > 0 device = nodes[0].get_device() self.current_device = device backend = self.get_backend(device) return backend.benchmark_fused_nodes(nodes) def finalize_multi_template_buffers(self) -> None: def replace_buffer( orig_node: ir.MultiTemplateBuffer, new_node: ir.Buffer ) -> None: replaced_name = new_node.name orig_name = orig_node.get_name() assert isinstance(orig_name, str) and isinstance(replaced_name, str) del V.graph.name_to_buffer[replaced_name] new_node.name = orig_name orig = V.graph.buffers.index(orig_node) V.graph.buffers.remove(new_node) V.graph.buffers[orig] = new_node V.graph.name_to_buffer[orig_name] = new_node for i, node in enumerate(self.nodes): if isinstance(node, SchedulerNode) and isinstance( node.node, ir.MultiTemplateBuffer ): multi_node = node.node min_node_unfused, _ = multi_node.get_min_choice() if isinstance( min_node_unfused, torch._inductor.ir.TritonTemplateCallerBase, ): node.node.finalize_as_triton_caller(min_node_unfused) continue out_tensorbox = min_node_unfused.output_node() out_storage = out_tensorbox.data assert isinstance(out_storage, ir.StorageBox) out_buffer = out_storage.data assert isinstance(out_buffer, ir.Buffer) out_buffer.layout = multi_node.layout replace_buffer(multi_node, out_buffer) new_scheduler_node = self.create_scheduler_node(out_buffer) self.nodes[i] = new_scheduler_node self.name_to_node[node.get_name()] = new_scheduler_node self.name_to_fused_node[node.get_name()] = new_scheduler_node new_scheduler_node.users = node.users new_scheduler_node.min_order = node.min_order new_scheduler_node.max_order = node.max_order new_scheduler_node.last_usage = node.last_usage for user in new_scheduler_node.users: user.node.inverse_users.remove(node) user.node.inverse_users.append(new_scheduler_node) def speedup_by_fusion( self, node1: BaseSchedulerNode, node2: BaseSchedulerNode ) -> bool: """ If config.benchmark_fusion is False, always return True. Otherwise, return True if fusion can brings speedup. """ is_multi_template = node1.is_template() and isinstance( node1.get_template_node(), ir.MultiTemplateBuffer ) if not config.benchmark_fusion and not is_multi_template: return True if ( node1.is_template() and not isinstance(node1.get_template_node(), ir.TritonTemplateBuffer) or node1.is_foreach() or node2.is_foreach() ): # TODO support benchmarking epilogue fusion return True node_list_1 = node1.get_nodes() device = node_list_1[0].get_device() # don't support benchmark fusion for CPU right now. if device.type == "cpu": return True node_list_2 = node2.get_nodes() node_list_fused = list(itertools.chain(node_list_1, node_list_2)) # We can not accurately benchmark kernel using atomic_add # due to how we generate random integer inputs. # Skip benchmarking them by allowing fusion. if any( hasattr(n.node, "data") and n.node is not None and hasattr(n.node.data, "scatter_mode") and n.node.data.scatter_mode == "atomic_add" for n in node_list_fused ): return True from triton.compiler.errors import CompilationError why = WhyNoFuse(node1, node2) def log_fusion(ms_fused: float, ms1: float, ms2: float) -> None: if fusion_log.isEnabledFor(logging.DEBUG): if ms_fused < ms1 + ms2: fusion_log.debug( "can fuse (benchmark): fusing %s with %s cause %sx speedup", node1.get_names(), node2.get_names(), green_text(f"{(ms1 + ms2) / ms_fused:.3f}"), ) else: fusion_log.debug( "cannot fuse (benchmark): fusing %s with %s cause %sx slowdown", node1.get_names(), node2.get_names(), red_text(f"{ms_fused / (ms1 + ms2):.3f}"), ) if isinstance(node1, SchedulerNode) and isinstance( node1.node, ir.MultiTemplateBuffer ): multi_node = node1.node choice_timings = multi_node.choice_timings _, ms1 = multi_node.get_min_choice() ms2, path2 = self.benchmark_fused_nodes(node_list_2) min_ms_fused = float("inf") ms_fused_choice = None triton_choices = 0 for choice, unfused_time in choice_timings.items(): if not isinstance(choice, torch._inductor.ir.TritonTemplateCallerBase): continue if unfused_time >= ms1 + ms2: continue triton_choices += 1 if triton_choices > config.max_epilogue_benchmarked_choices: break # TODO - parallel compile triton templates # TODO - should prune/skip choices that are not within certain % of best choice with node1.node.swap_as_triton_caller(choice): ms_fused, _ = self.benchmark_fused_nodes(node_list_fused) if ms_fused < min_ms_fused: min_ms_fused = ms_fused ms_fused_choice = choice log_fusion(min_ms_fused, ms1, ms2) # after we do a fusion, we finalize a triton template. # TODO - could preserve multi template and choices for subsequent fusions if min_ms_fused < (ms1 + ms2) and ms_fused_choice is not None: node1.node.finalize_as_triton_caller(ms_fused_choice) return True else: return False else: try: ms1, path1 = self.benchmark_fused_nodes(node_list_1) if math.isinf(ms1): why("register spilling of the first kernel") return False ms2, path2 = self.benchmark_fused_nodes(node_list_2) if math.isinf(ms2): why("register spilling of the second kernel") return False ms_fused, path_fused = self.benchmark_fused_nodes(node_list_fused) if math.isinf(ms_fused): why("register spilling of the fused kernel") return False except CompilationError as e: # workaround triton issue: https://github.com/openai/triton/issues/2151 if "Loop-carried variable" in str(e): return True # allow fusion else: raise log_fusion(ms_fused, ms1, ms2) if ( is_metric_table_enabled("slow_fusion") and ms_fused >= ms1 + ms2 and (path1, path2) not in self.logged_slow_fusion ): self.logged_slow_fusion.add((path1, path2)) get_metric_table("slow_fusion").add_row( lambda: { "kernel1_path": path1, "kernel1_latency": ms1, "kernel2_path": path2, "kernel2_latency": ms2, "fused_kernel_path": path_fused, "fused_kernel_latency": ms_fused, "slow_down_ratio": ms_fused / (ms1 + ms2), } ) return ms_fused < ms1 + ms2 def fuse_nodes_once(self) -> None: """ Mutates self.nodes to combine nodes into FusedSchedulerNodes. This relies on two key functions to control the logic: - self.can_fuse(): checks if a fusion is legal - self.score_fusion(): assigns priority to a given fusion """ fused_nodes = set(self.nodes) for node1, node2 in self.get_possible_fusions(): node1 = self.name_to_fused_node[node1.get_first_name()] node2 = self.name_to_fused_node[node2.get_first_name()] if self.can_fuse(node1, node2) and not self.will_fusion_create_cycle( node1, node2 ): if not self.speedup_by_fusion(node1, node2): continue fusion_log.debug( "fusing %s with %s", node1.get_name(), node2.get_name() ) # above can_fuse asserts that node2 has the same device device = node1.get_device() node3 = self.get_backend(device).fuse(node1, node2) fused_nodes.remove(node1) fused_nodes.remove(node2) fused_nodes.add(node3) self.name_to_fused_node.update( {n.get_name(): node3 for n in node3.get_nodes()} ) self.nodes = sorted(fused_nodes, key=lambda x: x.min_order) self.topological_sort_schedule() self.prune_redundant_deps() def prune_redundant_deps(self) -> None: for node in self.nodes: node.prune_redundant_deps(self.name_to_fused_node) def get_possible_fusions(self) -> List[Tuple[BaseSchedulerNode, BaseSchedulerNode]]: """ Helper to find all legal fusion opportunities, sorted by self.score_fusion() """ possible_fusions = [] seen = set() def check_all_pairs(nodes: List[BaseSchedulerNode]) -> None: for node1_index, node1 in enumerate(nodes): for node2 in nodes[node1_index + 1 :]: key = (node1, node2) if key in seen: continue seen.add(key) if self.can_fuse(node1, node2): possible_fusions.append(key) elif (node2.is_template() or node2.is_foreach()) and self.can_fuse( node2, node1 ): # foreach fusions and epilogue fusions are order dependent possible_fusions.append((node2, node1)) buffer_names_grouping = collections.defaultdict(list) for node in self.nodes: for buf in node.used_buffer_names(): buffer_names_grouping[buf].append(node) for node_grouping in buffer_names_grouping.values(): check_all_pairs(node_grouping) if config.aggressive_fusion: group_grouping = collections.defaultdict(list) for node in self.nodes: group = getattr(node, "group", None) if group: group_grouping[group].append(node) for node_grouping in group_grouping.values(): check_all_pairs(node_grouping) possible_fusions = self.get_possible_fusions_with_highest_priority( possible_fusions ) possible_fusions.sort(key=self.score_fusion_key, reverse=True) fusion_log.debug("found %d possible fusions", len(possible_fusions)) return possible_fusions def will_fusion_create_cycle( self, node1: BaseSchedulerNode, node2: BaseSchedulerNode ) -> bool: """ Finds whether there's a path from node1 to node2 (or vice-versa) caused indirectly by other fusions. """ visited = set() def found_path(node: BaseSchedulerNode) -> bool: # only fused nodes can introduce new ancestors. if isinstance(node, FusedSchedulerNode) and node not in visited: visited.add(node) if node.get_names().issubset(combined_ancestors): # All fusion outputs are in ancestors of node1 and node2, thus # cannot introduce new path: # # 1. if output is neither descendent of node1 or node2, the # output cannot introduce a path # 2. due to [can_fuse]: if WLOG output is descendent of node1, it cannot be # on path(node1->node2), hence it cannot be ancestor of node2 # 3. due to [acyclic]: if WLOG output is descendent of node1, it cannot be # ancestor of node1 return False else: # continue DFS of new ancestors introduced by the fusion return bool(combined_names & node.ancestors) or any( found_path(self.name_to_fused_node[n]) for n in node.ancestors - combined_ancestors ) return False combined_names = node1.get_names() | node2.get_names() combined_ancestors = (node1.ancestors | node2.ancestors) - combined_names cycle = any(found_path(self.name_to_fused_node[n]) for n in combined_ancestors) if cycle: WhyNoFuse(node1, node2)("will create cycle") return cycle def can_fusion_increase_peak_memory( self, node1: BaseSchedulerNode, node2: BaseSchedulerNode ) -> bool: """ This function prevents fusion for nodes that can increase memory footprint. This problem is more common in horizontal fusion, where nodes that are far apart in the original order get fused, lengthening the live intervals of tensors. This is very evident in models with activation checkpointing, where the recomputed nodes from different checkpointed regions get fused and significantly increase the memory footprint. The current attempt is a quick, possibly hacky, heuristic to prevent the fusion of nodes that are far away in the original order. A better but difficult to implement heurisitic would be to use live intervals of the buffers, find region of peak pressure in the original program and prevent fusion that crosses that peak region. We might need special care or good approximation in this implementation, as fusion of node changes live intervals, and re-computing live intervals and peak memory after each fusion can introduce large compilation overhead. """ proximity_score = max( abs(node1.min_order - node2.max_order), abs(node2.min_order - node1.max_order), ) return proximity_score > 64 def decide_fusion_fail_reason( self, node1: BaseSchedulerNode, node2: BaseSchedulerNode, common_buf_names: Tuple[str, ...], ) -> str: """ Try to decide reasons why fusion fail due to no shared memory even though there are common buffers. """ reasons = {} node1_name2dep = {dep.name: dep for dep in node1.read_writes.reads_and_writes()} node2_name2dep = {dep.name: dep for dep in node2.read_writes.reads_and_writes()} for buf_name in common_buf_names: buf = V.graph.get_buffer(buf_name) lhs_dep = node1_name2dep[buf_name] rhs_dep = node2_name2dep[buf_name] if lhs_dep.get_numel() != rhs_dep.get_numel(): reasons[ buf_name ] = f"different numel: {lhs_dep.get_numel()} v.s. {rhs_dep.get_numel()}" continue # same numel but different MemoryDep.size. Should be broadcasting if sympy_product(lhs_dep.size) != sympy_product(rhs_dep.size): reasons[buf_name] = "broadcast" continue if not isinstance(lhs_dep, MemoryDep) or not isinstance(rhs_dep, MemoryDep): reasons[ buf_name ] = f"not MemoryDep: {type(lhs_dep)} v.s. {type(rhs_dep)}" continue lhs_off = lhs_dep.get_offset() rhs_off = rhs_dep.get_offset() if lhs_off != rhs_off: # One example is in transformer, we use a concatenated linear layer # to project Q/K/V and then split the result. The 3 splits will # point to the same buffer with different offsets. reasons[buf_name] = f"different offset: {lhs_off} v.s. {rhs_off}" continue if ( lhs_dep.normalize_with_stride_order() == rhs_dep.normalize_with_stride_order() ): reasons[buf_name] = f"Mismatch loop orders: {lhs_dep} v.s. {rhs_dep}" continue # Add more rules here reasons[ buf_name ] = f"Unknown reason: {lhs_dep} v.s. {rhs_dep}. Layout: {buf.layout}" return str(reasons) def can_fuse(self, node1: BaseSchedulerNode, node2: BaseSchedulerNode) -> bool: """ Determine if it is possible to combine node1 and node2 into a single fused node. """ if node1 is node2: return False why = WhyNoFuse(node1, node2) if ( isinstance(node1, (ExternKernelSchedulerNode, NopKernelSchedulerNode)) and not node1.is_template() ): why("node1 is extern or nop") return False if ( isinstance(node2, (ExternKernelSchedulerNode, NopKernelSchedulerNode)) and not node2.is_template() ): why("node2 is extern or nop") return False if node2.get_names() & node1.ancestors: why("node1 must go before node2") return False if node2.is_template(): why("templates can only fuse epilogues") return False if node1.is_template() and ( node2.has_aliasing_or_mutation() or node2.is_reduction() or not config.epilogue_fusion ): why("template epilogue not satisfied") return False device = node1.get_device() device2 = node2.get_device() if device != device2: why("device mismatch (%s vs %s)", device, device2) return False del device2 no_shared_data = self.score_fusion_memory(node1, node2) == 0 if no_shared_data and ( not config.aggressive_fusion or node1.is_reduction() or node2.is_reduction() ): if is_metric_table_enabled("fusion_failure_due_to_indexing_mismatch"): common_buf_names = ( node1.read_writes.buffer_names() & node2.read_writes.buffer_names() ) if len(common_buf_names) > 0: get_metric_table("fusion_failure_due_to_indexing_mismatch").add_row( lambda: { "pre_grad_graph_id": V.graph.graph_id, "post_grad_graph_id": V.graph.post_grad_graph_id, "node1_name": node1.get_name(), "node2_name": node2.get_name(), "node1_debug_str": write_text(node1.debug_str()), "node2_debug_str": write_text(node2.debug_str()), "common_buffer_names": list(common_buf_names), "failure_reason": self.decide_fusion_fail_reason( node1, node2, common_buf_names ), } ) why("no shared data due to indexing mismatch") return False why("no shared data") return False # heuristic not needed for correctness if ( not node1.is_foreach() and not node2.is_foreach() and len(node1.get_nodes()) + len(node2.get_nodes()) > config.max_fusion_size ): why("exceeds max fusion") return False # heuristic not needed for correctness if node1.get_names() & node2.ancestors: # node2 depends on node1 outputs if not self.can_fuse_vertical(node1, node2): return False return self.get_backend(device).can_fuse_vertical(node1, node2) else: # nodes don't depend on each other, but may have common reads if self.can_fusion_increase_peak_memory(node1, node2): why("will increase peak memory") return False return self.get_backend(device).can_fuse_horizontal(node1, node2) def can_fuse_vertical( self, node1: BaseSchedulerNode, node2: BaseSchedulerNode ) -> bool: """ Check if it is legal to fuse a consumer (node2) into a producer (node1). We can fuse them if all the reads of node2 either match corresponding writes in node1, or are written by nodes that can be scheduled before the fusion of node1 and node2. We also disable fusion of a write subsequent to a read if the reads and writes do not align. """ node1_names = node1.get_names() computed_deps = set() why = WhyNoFuse(node1, node2) for cd in node1.read_writes.writes: if not isinstance(cd, MemoryDep): continue for rd in node2.unmet_dependencies: if self.fusable_read_and_write(rd, cd): computed_deps.add(rd) remaining_deps = {dep.name for dep in node2.unmet_dependencies - computed_deps} if remaining_deps & node1_names: # MemoryDeps didn't match and read different locations of the same buffer. # Examples here include: # - MemoryDep("foo", x) != MemoryDep("foo", x + 1) # - MemoryDep("foo", x) != StarDep("foo") why("memory deps did not match") return False for name in remaining_deps: if node1_names & self.name_to_fused_node[name].ancestors: why("intermediate nodes between node1 & node2") return False # similar to can_inplace, if we are going to fuse a write subsequent to a read # require that the indexing and size is the same for write in node2.read_writes.writes: if not isinstance(write, MemoryDep): continue for read in node1.read_writes.reads: if write.name != self.mutation_renames.get(read.name, read.name): continue # bail on StarDep if not self.fusable_read_and_write(read, write): why("fusing a write into a read with different indexing formula") return False return True # StarDep doesn't match MemoryDep, different indices don't match # However, broadcasting sometimes strips dimensions, and if that's the case # we still can match unmet dep # if there's indirect indexing, don't match it def fusable_read_and_write(self, read: Dep, write: MemoryDep) -> bool: if isinstance(read, MemoryDep): if read.mode == write.mode and write.mode is not None: return True read_name = read.name if read_name in self.mutation_renames: read_name = self.mutation_renames[read_name] return ( read_name == write.name and not free_symbol_is_type(read.index, SymT.TMP) and not free_symbol_is_type(write.index, SymT.TMP) and read.index == write.index and len(read.size) >= len(write.size) and read.size[: len(write.size)] == write.size ) elif isinstance(read, StarDep): read_name = self.mutation_renames.get(read.name, read.name) write_name = self.mutation_renames.get(write.name, write.name) if ( read.mode == write.mode and write.mode is not None and read_name == write_name ): return True return False def score_fusion( self, node1: BaseSchedulerNode, node2: BaseSchedulerNode ) -> Tuple[bool, bool, int, int]: """ Assign a score (higher comes first) to the fusion of node1 and node2. When different fusions conflict with each other, this is the way we decide what order to run them in. Our current score is based on: - Estimate of the saved memory operations - Fusions closer together in original order """ memory_score = self.score_fusion_memory(node1, node2) proximity_score = -max( abs(node1.min_order - node2.max_order), abs(node2.min_order - node1.max_order), ) return ( node1.is_template() == config.epilogue_fusion_first and memory_score > 0, node1.is_reduction() == node2.is_reduction() and memory_score > 0, memory_score, proximity_score, ) def dep_size_hint(self, dep: Dep) -> int: res = 0 if dep not in self.__dep_size_hint_cache: try: if not dep.has_unbacked_symbols(): res = dep.numbytes_hint() except KeyError: # In at least one test (test/inductor/test_torchbind.py) we # create a StarDep that doesn't exist in the graph and calling # `has_unbacked_symbols()` throws an error. pass self.__dep_size_hint_cache[dep] = res else: res = self.__dep_size_hint_cache[dep] return res def score_fusion_memory( self, node1: BaseSchedulerNode, node2: BaseSchedulerNode ) -> int: """ The first term in our fusion score that estimates number of saved memory operations. """ common_memory_deps = (node1.read_writes.reads | node1.read_writes.writes) & ( node2.read_writes.reads | node2.read_writes.writes ) return sum(self.dep_size_hint(dep) for dep in common_memory_deps) def get_possible_fusions_with_highest_priority( self, possible_fusions: List[Tuple[BaseSchedulerNode, BaseSchedulerNode]] ) -> List[Tuple[BaseSchedulerNode, BaseSchedulerNode]]: # Group the possible fusions based on their priority from the backend. # Only return the group of possible fusions with highest priority. if len(possible_fusions) == 0: return possible_fusions possible_fusions_group_by_priority: Dict[ int, List[Tuple[BaseSchedulerNode, BaseSchedulerNode]] ] = {} for node1, node2 in possible_fusions: assert node1.get_device() == node2.get_device() device = node1.get_device() fusion_pair_priority = int( self.get_backend(device).get_fusion_pair_priority(node1, node2) ) if fusion_pair_priority not in possible_fusions_group_by_priority: possible_fusions_group_by_priority[fusion_pair_priority] = [ (node1, node2), ] else: possible_fusions_group_by_priority[fusion_pair_priority].append( (node1, node2) ) # return the possible fusions with highest priority possible_fusions_with_highest_priority = min( possible_fusions_group_by_priority.items(), key=operator.itemgetter(0) )[1] assert len(possible_fusions_with_highest_priority) > 0 return possible_fusions_with_highest_priority def score_fusion_key( self, nodes: Tuple[BaseSchedulerNode, BaseSchedulerNode] ) -> Tuple[bool, bool, int, int]: """ Shim for list.sort(key=...) """ node1, node2 = nodes return self.score_fusion(node1, node2) def compute_last_usage(self) -> None: """ Populate node.last_usage recursively (also for the nodes within a FusedSchedulerNode) """ future_used_buffers = set(V.graph.get_output_names()) for node in reversed(self.nodes): node.set_last_usage(future_used_buffers, self.mutation_real_name) future_used_buffers.update(node.last_usage) def free_buffers(self) -> None: """Free any buffers that are no longer needed""" for name in sorted( self.buffer_names_to_free - V.graph.removed_buffers - V.graph.wrapper_code.freed ): if name in self.name_to_node: node = self.name_to_node[name] if node.can_free(): V.graph.wrapper_code.codegen_free(node.node) elif name in V.graph.graph_inputs: storage = V.graph.graph_inputs[name].data assert isinstance(storage, ir.StorageBox) and storage.is_input_buffer() V.graph.wrapper_code.codegen_free(storage.data) self.buffer_names_to_free.clear() def remove_kernel_local_buffers(self) -> None: """ Any buffers that are both created and have a last use in the same kernel can be removed. """ # V.kernel.store_buffer_names should represent the set of nodes # get fused fused_node_names = V.kernel.store_buffer_names names_to_remove = [] for out_buf in V.kernel.store_buffer_names: users = self.name_to_node[out_buf].users assert users is not None users = {user.get_name() for user in users if not user.is_weak} if users.issubset(fused_node_names): names_to_remove.append(out_buf) def remove_filter(n: str) -> bool: return ( n not in V.kernel.must_keep_buffers and n not in V.kernel.args.input_buffers and n not in self.mutation_renames and n not in self.mutation_real_name ) names_to_remove = list(filter(remove_filter, names_to_remove)) for name in names_to_remove: if name in V.kernel.args.inplace_buffers: buf = V.kernel.args.inplace_buffers[name] if isinstance(buf, str) and buf.startswith("REMOVED"): continue remove = all(n in names_to_remove for n in buf.other_names) if remove: self.remove_inplace_buffer(name) V.kernel.inplaced_to_remove.add(name) else: self.remove_buffer(name) def remove_buffer(self, name: str) -> None: # Assign a special value instead of deleting the entry # because we still rely on output_buffers's length to # generate unique arg name. log.debug("remove_buffer(%r)", name) V.kernel.args.output_buffers[name] = "REMOVED" V.kernel.removed_buffers.add(name) def remove_inplace_buffer(self, name: str) -> None: log.debug("removing_inplace_buffer(%r)", name) inner_name = V.kernel.args.inplace_buffers[name].inner_name V.kernel.args.inplace_buffers[name] = inner_name.replace( "in_out_ptr", "REMOVED" ) V.kernel.removed_buffers.add(name) def flush(self) -> None: for backend in self.backends.values(): backend.flush() self.free_buffers() def codegen_extern_call(self, scheduler_node: ExternKernelSchedulerNode) -> None: assert isinstance(scheduler_node, ExternKernelSchedulerNode) # 'decide_inplace_update' stores the inplace update decisions in # the current kernel from where 'allocate' retrieve those decisions. # We have to make sure there is a non-NULL kernel handler to store # those inplace update decisions. counters["inductor"]["extern_calls"] += 1 with V.set_kernel_handler(Kernel(increase_kernel_count=False)): scheduler_node.decide_inplace_update() scheduler_node.allocate() node = scheduler_node.node assert isinstance(node, ir.ExternKernel), f"{type(node)=}" node.codegen(V.graph.wrapper_code) self.free_buffers() def create_backend(self, device: torch.device) -> "BaseScheduling": assert ( not is_gpu(device.type) or device.index is not None ), f"{device} should have been normalized in lowering" V.graph.add_device_info(device) device_scheduling = get_scheduling_for_device(device.type) if device_scheduling is None: raise RuntimeError(f"Unsupported device type: {device.type}") if not has_triton(): if ( device.type == "cuda" and (device_props := torch.cuda.get_device_properties(device)).major < 7 ): raise RuntimeError( f"Found {device_props.name} which is too old to be supported by the triton GPU compiler, which is used as the backend. Triton only supports devices of CUDA Capability >= 7.0, but your device is of CUDA capability {device_props.major}.{device_props.minor}" # noqa: B950 ) elif is_gpu(device.type): raise RuntimeError( "Cannot find a working triton installation. More information on installing Triton can be found at https://github.com/openai/triton" # noqa: B950 ) return device_scheduling(self) def get_backend(self, device: torch.device) -> "BaseScheduling": if device not in self.backends: self.backends[device] = self.create_backend(device) return self.backends[device] def enter_context(self, node: BaseSchedulerNode) -> None: def get_order(n: torch.fx.Node) -> int: if n not in self.origin_to_index: self.origin_to_index.update({n: i for i, n in enumerate(n.graph.nodes)}) return self.origin_to_index[n] # Use a dict to have ordering origins = { (get_order(e), e): None for n in node.get_nodes() if n.node is not None for e in n.node.origins } origins = list(origins.keys()) if origins: _, last = max(origins, key=operator.itemgetter(0)) V.graph.wrapper_code.enter_context(last) @dynamo_timed def codegen(self) -> None: for node in self.nodes: try: log.debug( "Generating code for node %s with estimated runtime %f", node.get_name(), node.get_estimated_runtime(), ) except Exception as e: log.debug( "Generating code for node %s with estimated runtime 0.0", node.get_name(), ) self.enter_context(node) if not isinstance(node, NopKernelSchedulerNode) and ( device := node.get_device() ): if ( device != self.current_device or node.is_extern() or node.is_template() ): self.flush() if device != self.current_device: if self.current_device and device_need_guard( self.current_device.type ): V.graph.wrapper_code.codegen_device_guard_exit() if device_need_guard(device.type): assert device.index is not None, "device should have an index" V.graph.wrapper_code.codegen_device_guard_enter(device.index) self.current_device = device self.buffer_names_to_free.update(node.last_usage) if node.is_template(): node, *epilogue = node.get_nodes() self.get_backend(device).codegen_template(node, epilogue) elif node.is_extern(): node = typing.cast(ExternKernelSchedulerNode, node) self.codegen_extern_call(node) elif node.is_foreach(): node = typing.cast(ForeachKernelSchedulerNode, node) backend_ = self.get_backend(device) from .codegen.cuda_combined_scheduling import CUDACombinedScheduling from .codegen.simd import SIMDScheduling if isinstance(backend_, (SIMDScheduling, CUDACombinedScheduling)): backend = backend_ else: raise AssertionError(f"{type(self)=}") backend.codegen_foreach(node) elif isinstance(node, (FusedSchedulerNode, SchedulerNode)): self.get_backend(device).codegen_node(node) else: assert isinstance(node, NopKernelSchedulerNode) node.allocate() if config.triton.debug_sync_kernel: self.get_backend(device).codegen_sync() self.available_buffer_names.update(node.get_names()) if not isinstance(node, NopKernelSchedulerNode): device = node.get_device() if device is not None and self.get_backend(device).ready_to_flush(): self.flush() if self.current_device and device_need_guard(self.current_device.type): # exit the outermost CUDA device guard. this is # important for nested indentation codegen-ing. V.graph.wrapper_code.codegen_device_guard_exit() self.flush() def get_buffer_layout(self, buf_name: str) -> ir.Layout: node = self.name_to_node[buf_name] assert node.node is not None return node.node.get_layout() class BaseScheduling: def can_fuse_vertical( self, node1: BaseSchedulerNode, node2: BaseSchedulerNode ) -> bool: """ Check whether node1 and node2 can be vertically fused or not. """ raise NotImplementedError def can_fuse_horizontal( self, node1: BaseSchedulerNode, node2: BaseSchedulerNode ) -> bool: """ Check whether node1 and node2 can be horizontally fused or not. """ raise NotImplementedError def fuse( self, node1: BaseSchedulerNode, node2: BaseSchedulerNode ) -> FusedSchedulerNode: """ Fuse two nodes """ if node1.is_foreach() or node2.is_foreach(): return ForeachKernelSchedulerNode.fuse(node1, node2) else: return FusedSchedulerNode.fuse(node1, node2) def group_fn( self, sizes: Sequence[Sequence[sympy.Expr]] ) -> Tuple[Tuple[sympy.Expr, ...], ...]: """ Process the iteration sizes in case a transformation needs to be applied. """ raise NotImplementedError def codegen_template( self, template_node: BaseSchedulerNode, epilogue_nodes: Sequence[BaseSchedulerNode], ) -> Optional[str]: """ Given a template node, generate a kernel. This function is only available for triton now. If the third-party backend behaves as a sub-class of TritonScheduling, it can override it or reuse it. """ raise NotImplementedError def codegen_node(self, node: Union[FusedSchedulerNode, SchedulerNode]) -> None: """ Generate a kernel given a list of pre-fused nodes. """ raise NotImplementedError def codegen_sync(self) -> None: """ Generate synchronization code for the kernel. This method depends on the hardware characteristics. """ raise NotImplementedError def ready_to_flush(self) -> bool: """ Check whether the backend is requesting the scheduler to flush the generated kernel. If not supported, please return False. """ return False def flush(self) -> None: """ Flush the generated kernel and python wrapper code to the source code file. """ raise NotImplementedError def benchmark_fused_nodes( self, nodes: Sequence[BaseSchedulerNode] ) -> Tuple[float, str]: """ Benchmark fused list of nodes and return the execution time in milliseconds on randomly generated inputs. """ raise NotImplementedError def get_fusion_pair_priority( self, node1: BaseSchedulerNode, node2: BaseSchedulerNode ) -> int: """ Return an unsigned integer which represents the priority of this fusion pair. The smaller is with higher priority. """ return 0 def debug_triton_code(node: Union[SchedulerNode, FusedSchedulerNode]) -> List[str]: lines = [] multi_template = node.get_template_node() assert multi_template is None or isinstance(multi_template, ir.MultiTemplateBuffer) if multi_template and multi_template.make_kernel_render is None: lines.append(f"{node.get_name()} Unfinalized multi template buffer") else: from torch._inductor.codegen.cuda_combined_scheduling import ( CUDACombinedScheduling, ) from torch._inductor.codegen.triton import TritonScheduling snodes = (node,) if isinstance(node, SchedulerNode) else node.snodes device = snodes[0].get_device() backend = node.scheduler.get_backend(device) assert isinstance(backend, (TritonScheduling, CUDACombinedScheduling)) V.graph.scheduler.current_device = device # Don't increment kernel count when generating debug string. # This will confuse some unit tests that check the number of # generated kernels. old_generated_kernel_count = metrics.generated_kernel_count triton_code = backend.generate_kernel_code_from_nodes(snodes).strip() metrics.generated_kernel_count = old_generated_kernel_count lines.append(f"{node.get_name()} Triton code:") lines.append(textwrap.indent(triton_code, " ")) return lines