python.control-flow

dynamic_shape_if_guard

Note

Tags: python.control-flow, torch.dynamic-shape

Support Level: SUPPORTED

Original source code:

# mypy: allow-untyped-defs
import torch



class DynamicShapeIfGuard(torch.nn.Module):
    """
    `if` statement with backed dynamic shape predicate will be specialized into
    one particular branch and generate a guard. However, export will fail if the
    the dimension is marked as dynamic shape from higher level API.
    """

    def forward(self, x):
        if x.shape[0] == 3:
            return x.cos()

        return x.sin()

Result:

ExportedProgram:
    class GraphModule(torch.nn.Module):
        def forward(self, x: "f32[3, 2, 2]"):
                cos: "f32[3, 2, 2]" = torch.ops.aten.cos.default(x);  x = None
            return (cos,)

Graph signature: ExportGraphSignature(input_specs=[InputSpec(kind=<InputKind.USER_INPUT: 1>, arg=TensorArgument(name='x'), target=None, persistent=None)], output_specs=[OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='cos'), target=None)])
Range constraints: {}

list_unpack

Note

Tags: python.data-structure, python.control-flow

Support Level: SUPPORTED

Original source code:

# mypy: allow-untyped-defs
from typing import List

import torch



class ListUnpack(torch.nn.Module):
    """
    Lists are treated as static construct, therefore unpacking should be
    erased after tracing.
    """

    def __init__(self):
        super().__init__()

    def forward(self, args: List[torch.Tensor]):
        """
        Lists are treated as static construct, therefore unpacking should be
        erased after tracing.
        """
        x, *y = args
        return x + y[0]

Result:

ExportedProgram:
    class GraphModule(torch.nn.Module):
        def forward(self, args_0: "f32[3, 2]", args_1: "i64[]", args_2: "i64[]"):
                add: "f32[3, 2]" = torch.ops.aten.add.Tensor(args_0, args_1);  args_0 = args_1 = None
            return (add,)

Graph signature: ExportGraphSignature(input_specs=[InputSpec(kind=<InputKind.USER_INPUT: 1>, arg=TensorArgument(name='args_0'), target=None, persistent=None), InputSpec(kind=<InputKind.USER_INPUT: 1>, arg=TensorArgument(name='args_1'), target=None, persistent=None), InputSpec(kind=<InputKind.USER_INPUT: 1>, arg=TensorArgument(name='args_2'), target=None, persistent=None)], output_specs=[OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add'), target=None)])
Range constraints: {}

static_for_loop

Note

Tags: python.control-flow

Support Level: SUPPORTED

Original source code:

# mypy: allow-untyped-defs
import torch



class StaticForLoop(torch.nn.Module):
    """
    A for loop with constant number of iterations should be unrolled in the exported graph.
    """

    def __init__(self):
        super().__init__()

    def forward(self, x):
        ret = []
        for i in range(10):  # constant
            ret.append(i + x)
        return ret

Result:

ExportedProgram:
    class GraphModule(torch.nn.Module):
        def forward(self, x: "f32[3, 2]"):
                add: "f32[3, 2]" = torch.ops.aten.add.Tensor(x, 0)
            add_1: "f32[3, 2]" = torch.ops.aten.add.Tensor(x, 1)
            add_2: "f32[3, 2]" = torch.ops.aten.add.Tensor(x, 2)
            add_3: "f32[3, 2]" = torch.ops.aten.add.Tensor(x, 3)
            add_4: "f32[3, 2]" = torch.ops.aten.add.Tensor(x, 4)
            add_5: "f32[3, 2]" = torch.ops.aten.add.Tensor(x, 5)
            add_6: "f32[3, 2]" = torch.ops.aten.add.Tensor(x, 6)
            add_7: "f32[3, 2]" = torch.ops.aten.add.Tensor(x, 7)
            add_8: "f32[3, 2]" = torch.ops.aten.add.Tensor(x, 8)
            add_9: "f32[3, 2]" = torch.ops.aten.add.Tensor(x, 9);  x = None
            return (add, add_1, add_2, add_3, add_4, add_5, add_6, add_7, add_8, add_9)

Graph signature: ExportGraphSignature(input_specs=[InputSpec(kind=<InputKind.USER_INPUT: 1>, arg=TensorArgument(name='x'), target=None, persistent=None)], output_specs=[OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add'), target=None), OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add_1'), target=None), OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add_2'), target=None), OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add_3'), target=None), OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add_4'), target=None), OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add_5'), target=None), OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add_6'), target=None), OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add_7'), target=None), OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add_8'), target=None), OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add_9'), target=None)])
Range constraints: {}

static_if

Note

Tags: python.control-flow

Support Level: SUPPORTED

Original source code:

# mypy: allow-untyped-defs
import torch



class StaticIf(torch.nn.Module):
    """
    `if` statement with static predicate value should be traced through with the
    taken branch.
    """

    def __init__(self):
        super().__init__()

    def forward(self, x):
        if len(x.shape) == 3:
            return x + torch.ones(1, 1, 1)

        return x

Result:

ExportedProgram:
    class GraphModule(torch.nn.Module):
        def forward(self, x: "f32[3, 2, 2]"):
                ones: "f32[1, 1, 1]" = torch.ops.aten.ones.default([1, 1, 1], device = device(type='cpu'), pin_memory = False)
            add: "f32[3, 2, 2]" = torch.ops.aten.add.Tensor(x, ones);  x = ones = None
            return (add,)

Graph signature: ExportGraphSignature(input_specs=[InputSpec(kind=<InputKind.USER_INPUT: 1>, arg=TensorArgument(name='x'), target=None, persistent=None)], output_specs=[OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='add'), target=None)])
Range constraints: {}