Source code for torch.cuda.graphs
# mypy: allow-untyped-defs
import gc
import typing
import torch
from .._utils import _dummy_type
if not hasattr(torch._C, "_CudaStreamBase"):
# Define dummy base classes
torch._C.__dict__["_CUDAGraph"] = _dummy_type("_CUDAGraph")
torch._C.__dict__["_graph_pool_handle"] = _dummy_type("_graph_pool_handle")
torch._C.__dict__["_cuda_isCurrentStreamCapturing"] = _dummy_type(
"_cuda_isCurrentStreamCapturing"
)
from torch._C import ( # noqa: F401
_cuda_isCurrentStreamCapturing,
_CUDAGraph,
_graph_pool_handle,
)
[docs]def is_current_stream_capturing():
r"""Return True if CUDA graph capture is underway on the current CUDA stream, False otherwise.
If a CUDA context does not exist on the current device, returns False without initializing the context.
"""
return _cuda_isCurrentStreamCapturing()
# Python shim helps Sphinx process docstrings more reliably.
[docs]def graph_pool_handle():
r"""Return an opaque token representing the id of a graph memory pool.
See :ref:`Graph memory management<graph-memory-management>`.
.. warning::
This API is in beta and may change in future releases.
"""
return _graph_pool_handle()
# Python shim helps Sphinx process docstrings more reliably.
[docs]class CUDAGraph(torch._C._CUDAGraph):
r"""Wrapper around a CUDA graph.
.. warning::
This API is in beta and may change in future releases.
"""
def __new__(cls):
return super().__new__(cls)
[docs] def capture_begin(self, pool=None, capture_error_mode="global"):
r"""Begin capturing CUDA work on the current stream.
Typically, you shouldn't call ``capture_begin`` yourself.
Use :class:`~torch.cuda.graph` or :func:`~torch.cuda.make_graphed_callables`,
which call ``capture_begin`` internally.
Arguments:
pool (optional): Token (returned by :func:`~torch.cuda.graph_pool_handle` or
:meth:`other_Graph_instance.pool()<torch.cuda.CUDAGraph.pool>`) that hints this graph may share memory
with the indicated pool. See :ref:`Graph memory management<graph-memory-management>`.
capture_error_mode (str, optional): specifies the cudaStreamCaptureMode for the graph capture stream.
Can be "global", "thread_local" or "relaxed". During cuda graph capture, some actions, such as cudaMalloc,
may be unsafe. "global" will error on actions in other threads, "thread_local" will only error for
actions in the current thread, and "relaxed" will not error on these actions. Do NOT change this setting
unless you're familiar with `cudaStreamCaptureMode <https://docs.nvidia.com/cuda/cuda-runtime-api/group__CUDART__STREAM.html#group__CUDART__STREAM_1g9d0535d93a214cbf126835257b16ba85>`_
""" # noqa: B950
super().capture_begin(pool=pool, capture_error_mode=capture_error_mode)
[docs] def capture_end(self):
r"""End CUDA graph capture on the current stream.
After ``capture_end``, ``replay`` may be called on this instance.
Typically, you shouldn't call ``capture_end`` yourself.
Use :class:`~torch.cuda.graph` or :func:`~torch.cuda.make_graphed_callables`,
which call ``capture_end`` internally.
"""
super().capture_end()
[docs] def pool(self):
r"""Return an opaque token representing the id of this graph's memory pool.
This id can optionally be passed to another graph's ``capture_begin``,
which hints the other graph may share the same memory pool.
"""
return super().pool()
[docs] def enable_debug_mode(self):
r"""Enable debugging mode for CUDAGraph.debug_dump."""
return super().enable_debug_mode()
[docs] def debug_dump(self, debug_path):
r"""
Arguments:
debug_path (required): Path to dump the graph to.
Calls a debugging function to dump the graph if the debugging is
enabled via CUDAGraph.enable_debug_mode()
"""
return super().debug_dump(debug_path)
[docs]class graph:
r"""Context-manager that captures CUDA work into a :class:`torch.cuda.CUDAGraph` object for later replay.
See :ref:`CUDA Graphs <cuda-graph-semantics>` for a general introduction,
detailed use, and constraints.
Arguments:
cuda_graph (torch.cuda.CUDAGraph): Graph object used for capture.
pool (optional): Opaque token (returned by a call to :func:`~torch.cuda.graph_pool_handle()` or
:meth:`other_Graph_instance.pool()<torch.cuda.CUDAGraph.pool>`) hinting this graph's capture
may share memory from the specified pool. See :ref:`Graph memory management<graph-memory-management>`.
stream (torch.cuda.Stream, optional): If supplied, will be set as the current stream in the context.
If not supplied, ``graph`` sets its own internal side stream as the current stream in the context.
capture_error_mode (str, optional): specifies the cudaStreamCaptureMode for the graph capture stream.
Can be "global", "thread_local" or "relaxed". During cuda graph capture, some actions, such as cudaMalloc,
may be unsafe. "global" will error on actions in other threads, "thread_local" will only error for
actions in the current thread, and "relaxed" will not error on actions. Do NOT change this setting
unless you're familiar with `cudaStreamCaptureMode <https://docs.nvidia.com/cuda/cuda-runtime-api/group__CUDART__STREAM.html#group__CUDART__STREAM_1g9d0535d93a214cbf126835257b16ba85>`_
.. note::
For effective memory sharing, if you pass a ``pool`` used by a previous capture and the previous capture
used an explicit ``stream`` argument, you should pass the same ``stream`` argument to this capture.
.. warning::
This API is in beta and may change in future releases.
.. _cudaStreamCaptureMode:
https://docs.nvidia.com/cuda/cuda-runtime-api/group__CUDART__STREAM.html#group__CUDART__STREAM_1g9d0535d93a214cbf126835257b16ba85
""" # noqa: B950
default_capture_stream: typing.Optional["torch.cuda.Stream"] = None
def __init__(
self,
cuda_graph,
pool=None,
stream=None,
capture_error_mode: str = "global",
):
# Lazy-init of default_capture_stream helps avoid circular-import errors.
# Not thread safe, but graphs already have the general (explicitly documented)
# restriction that only one capture may be underway at a time in the process.
if self.__class__.default_capture_stream is None:
self.__class__.default_capture_stream = torch.cuda.Stream()
self.pool = () if pool is None else (pool,)
self.capture_stream = (
stream if stream is not None else self.__class__.default_capture_stream
)
assert self.capture_stream is not None
self.stream_ctx = torch.cuda.stream(self.capture_stream)
self.cuda_graph = cuda_graph
self.capture_error_mode = capture_error_mode
def __enter__(self):
# Free as much memory as we can for the graph
torch.cuda.synchronize()
gc.collect()
torch.cuda.empty_cache()
# Stackoverflow seems comfortable with this pattern
# https://stackoverflow.com/questions/26635684/calling-enter-and-exit-manually#39172487
self.stream_ctx.__enter__()
self.cuda_graph.capture_begin(
*self.pool, capture_error_mode=self.capture_error_mode
)
def __exit__(self, exc_type, exc_value, traceback):
self.cuda_graph.capture_end()
self.stream_ctx.__exit__(exc_type, exc_value, traceback)
# returning None should propagate exceptions from either capture_end or stream_ctx.__exit__()
[docs]def make_graphed_callables(
callables, sample_args, num_warmup_iters=3, allow_unused_input=False, pool=None
):
r"""Accept callables (functions or :class:`nn.Module<torch.nn.Module>`\ s) and returns graphed versions.
Each graphed callable's forward pass runs its source callable's
forward CUDA work as a CUDA graph inside a single autograd node.
The graphed callable's forward pass also appends
a backward node to the autograd graph. During backward, this node runs the
callable's backward work as a CUDA graph.
Therefore, each graphed callable should be a drop-in replacement for its source callable
in an autograd-enabled training loop.
See :ref:`Partial-network capture<partial-network-capture>` for detailed use and constraints.
If you pass a tuple of several callables, their captures will use the same memory pool.
See :ref:`Graph memory management<graph-memory-management>` for when this is appropriate.
Arguments:
callables (torch.nn.Module or Python function, or tuple of these): Callable or callables to graph.
See :ref:`Graph memory management<graph-memory-management>` for when passing a tuple of callables
is appropriate. If you pass a tuple of callables, their order in the tuple must be the same order
they'll run in the live workload.
sample_args (tuple of Tensors, or tuple of tuples of Tensors): Samples args for each callable.
If a single callable was passed, ``sample_args`` must be a single tuple of argument Tensors.
If a tuple of callables was passed, ``sample_args`` must be tuple of tuples of argument Tensors.
num_warmup_iters (int): The number of warmup iterations. Currently, ``DataDistributedParallel`` needs
11 iterations for warm up. Default: ``3``.
allow_unused_input (bool): If False, specifying inputs that were not used when computing outputs
(and therefore their grad is always zero) is an error. Defaults to False.
pool (optional): Token (returned by :func:`~torch.cuda.graph_pool_handle` or
:meth:`other_Graph_instance.pool()<torch.cuda.CUDAGraph.pool>`) that hints this graph may share memory
with the indicated pool. See :ref:`Graph memory management<graph-memory-management>`.
.. note::
The ``requires_grad`` state of each Tensor in ``sample_args`` must match the state
that's expected for the corresponding real input in the training loop.
.. warning::
This API is in beta and may change in future releases.
.. warning::
``sample_args`` for each callable must contain only Tensors. Other types are not allowed.
.. warning::
Returned callables do not support higher order differentiation (e.g., double backward).
.. warning::
In any :class:`~torch.nn.Module` passed to :func:`~make_graphed_callables`, only parameters
may be trainable. Buffers must have ``requires_grad=False``.
.. warning::
After you pass a :class:`torch.nn.Module` through :func:`~make_graphed_callables`,
you may not add or remove any of that Module's parameters or buffers.
.. warning::
:class:`torch.nn.Module`\s passed to :func:`~torch.cuda.make_graphed_callables` must not have module hooks
registered on them at the time they are passed. However, registering hooks on modules *after* passing them
through :func:`~torch.cuda.make_graphed_callables` is allowed.
.. warning::
When running a graphed callable, you must pass its arguments in the same order and format
they appeared in that callable's ``sample_args``.
.. warning::
The automatic mixed precision is supported in :func:`~torch.cuda.make_graphed_callables` only with disabled
caching. The context manager `torch.cuda.amp.autocast()` must have `cache_enabled=False`.
"""
if torch.is_autocast_enabled() and torch.is_autocast_cache_enabled():
raise RuntimeError(
"make_graphed_callables does not support the autocast caching. Please set `cache_enabled=False`."
)
just_one_callable = False
if not isinstance(callables, tuple):
just_one_callable = True
callables = (callables,)
sample_args = (sample_args,)
flatten_sample_args = []
for c, args in zip(callables, sample_args):
if isinstance(c, torch.nn.Module):
assert (
len(c._backward_hooks) == 0
and len(c._forward_hooks) == 0
and len(c._forward_pre_hooks) == 0
), (
"Modules must not have hooks registered at the time they are passed. However, registering hooks "
+ "on modules after passing them through make_graphed_callables is allowed."
)
assert all(b.requires_grad is False for b in c.buffers()), (
"In any :class:`~torch.nn.Module` passed to "
+ ":func:`~make_graphed_callables`, only parameters may be trainable. All buffers must have "
+ "``requires_grad=False``."
)
flatten_arg = torch.utils._pytree.arg_tree_leaves(*args)
flatten_sample_args.append(tuple(flatten_arg))
assert all(isinstance(arg, torch.Tensor) for arg in flatten_arg), (
"In the beta API, sample_args "
+ "for each callable must contain only Tensors. Other types are not allowed."
)
# If a callable is an nn.Module, its graph's full input surface is the args the user explicitly
# passes to forward (ie, its sample_args) AND the module's parameter attributes.
per_callable_len_user_args = [len(args) for args in flatten_sample_args]
per_callable_module_params = [
tuple(c.parameters()) if isinstance(c, torch.nn.Module) else ()
for c in callables
]
per_callable_static_input_surfaces = [
flatten_sample_args[i] + per_callable_module_params[i]
for i in range(len(callables))
]
fwd_graphs = [torch.cuda.CUDAGraph() for _ in range(len(callables))]
bwd_graphs = [torch.cuda.CUDAGraph() for _ in range(len(callables))]
mempool = graph_pool_handle() if pool is None else pool
# Warmup
# Hopefully prevents cudnn benchmarking and other lazy-initialization cuda work
# from ending up in any captures.
torch.cuda.synchronize()
with torch.cuda.stream(torch.cuda.Stream()):
for func, args, static_input_surface in zip(
callables, sample_args, per_callable_static_input_surfaces
):
grad_inputs, outputs, outputs_grad = None, None, None
for _ in range(num_warmup_iters):
outputs = torch.utils._pytree.tree_leaves(func(*args))
outputs_grad = tuple(o for o in outputs if o.requires_grad)
if len(outputs_grad) > 0:
grad_inputs = torch.autograd.grad(
outputs=outputs_grad,
inputs=tuple(
i for i in static_input_surface if i.requires_grad
),
grad_outputs=tuple(
torch.empty_like(o) for o in outputs if o.requires_grad
),
only_inputs=True,
allow_unused=allow_unused_input,
)
for v in [outputs, outputs_grad, grad_inputs]:
del v
torch.cuda.synchronize()
# All captures here share a mempool. To avoid replays corrupting each other's memory,
# the safest approach is to capture all passes in the same order they'll run:
# fwd 1, fwd 2, ... fwd N, then bwd N, bwd N-1, ... bwd 1.
# Capture forward graphs
per_callable_static_outputs = []
per_callable_output_unflatten_spec = []
for func, args, fwd_graph in zip(callables, sample_args, fwd_graphs):
with torch.cuda.graph(fwd_graph, pool=mempool):
outputs = func(*args)
flatten_outputs, spec = torch.utils._pytree.tree_flatten(outputs)
per_callable_static_outputs.append(tuple(flatten_outputs))
per_callable_output_unflatten_spec.append(spec)
# Capture backward graphs in reverse order
per_callable_static_grad_outputs = []
per_callable_static_grad_inputs = []
for static_input_surface, static_outputs, bwd_graph in zip(
reversed(per_callable_static_input_surfaces),
reversed(per_callable_static_outputs),
reversed(bwd_graphs),
):
# For now, assumes all static_outputs require grad
# assert all(o.requires_grad for o in static_outputs), "Outputs of graphed callables must require grad."
static_grad_outputs = tuple(
torch.empty_like(o) if o.requires_grad else None for o in static_outputs
)
outputs_grad = tuple(o for o in static_outputs if o.requires_grad)
grad_inputs = None
if len(outputs_grad) > 0:
with torch.cuda.graph(bwd_graph, pool=mempool):
grad_inputs = torch.autograd.grad(
outputs=outputs_grad,
inputs=tuple(i for i in static_input_surface if i.requires_grad),
grad_outputs=tuple(o for o in static_grad_outputs if o is not None),
only_inputs=True,
allow_unused=allow_unused_input,
)
# Constructs a tuple suitable for returning from Graphed.backward:
# Pads out the actually-needed grads with Nones in gradient slots for inputs that don't require grad.
# I couldn't think of a slick one-liner for this pattern.
static_grad_inputs = []
grad_idx = 0
for arg in static_input_surface:
if arg.requires_grad and grad_inputs is not None:
static_grad_inputs.append(grad_inputs[grad_idx])
grad_idx += 1
else:
static_grad_inputs.append(None) # type: ignore[arg-type]
static_grad_inputs = tuple(static_grad_inputs) # type: ignore[assignment]
per_callable_static_grad_outputs.append(static_grad_outputs)
per_callable_static_grad_inputs.append(static_grad_inputs)
# Reverses the most recent two lists
per_callable_static_grad_outputs.reverse()
per_callable_static_grad_inputs.reverse()
# Now for every per_callable list, per_callable_*[i] holds the stuff for the ith callable.
def make_graphed_autograd_function(
fwd_graph,
bwd_graph,
module_params,
len_user_args,
output_unflatten_spec,
static_input_surface,
static_outputs,
static_grad_outputs,
static_grad_inputs,
):
class Graphed(torch.autograd.Function):
@staticmethod
def forward(ctx, *inputs):
# At this stage, only the user args may (potentially) be new tensors.
for i in range(len_user_args):
if static_input_surface[i].data_ptr() != inputs[i].data_ptr():
static_input_surface[i].copy_(inputs[i])
fwd_graph.replay()
assert isinstance(static_outputs, tuple)
return tuple(o.detach() for o in static_outputs)
@staticmethod
@torch.autograd.function.once_differentiable
def backward(ctx, *grads):
assert len(grads) == len(static_grad_outputs)
for g, grad in zip(static_grad_outputs, grads):
if g is not None:
# don't copy if autograd gods have been kind and the
# incoming grad is already in the right place
if g.data_ptr() != grad.data_ptr():
g.copy_(grad)
bwd_graph.replay()
# Input args that didn't require grad expect a None gradient.
assert isinstance(static_grad_inputs, tuple)
return tuple(
b.detach() if b is not None else b for b in static_grad_inputs
)
def functionalized(*user_args):
# Runs the autograd function with inputs == all inputs to the graph that might require grad
# (explicit user args + module parameters)
# Assumes module params didn't change since capture.
flatten_user_args = torch.utils._pytree.arg_tree_leaves(*user_args)
out = Graphed.apply(*(tuple(flatten_user_args) + module_params))
return torch.utils._pytree.tree_unflatten(out, output_unflatten_spec)
return functionalized
# Put together the final graphed callables
ret = []
for i, func in enumerate(callables):
graphed = make_graphed_autograd_function(
fwd_graphs[i],
bwd_graphs[i],
per_callable_module_params[i],
per_callable_len_user_args[i],
per_callable_output_unflatten_spec[i],
per_callable_static_input_surfaces[i],
per_callable_static_outputs[i],
per_callable_static_grad_outputs[i],
per_callable_static_grad_inputs[i],
)
if isinstance(func, torch.nn.Module):
def make_graphed_forward(func, graph_training_state, graphed, orig_fwd):
def new_fwd(*user_args):
# If the module's training-or-eval state matches what we graphed,
# run the graph, otherwise run the original forward method
if func.training == graph_training_state:
return graphed(*user_args)
else:
return orig_fwd(*user_args)
return new_fwd
func.forward = make_graphed_forward(func, func.training, graphed, func.forward) # type: ignore[assignment]
ret.append(func)
else:
ret.append(graphed)
if just_one_callable:
return ret[0]
return tuple(ret)
