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ONNX 简介 || 将 PyTorch 模型导出到 ONNX || 扩展 ONNX 导出器的算子支持 || `将带有控制流的模型导出到 ONNX

将带有控制流的模型导出到 ONNX

作者Xavier Dupré

概述

本教程演示了在将 PyTorch 模型导出到 ONNX 时如何处理控制流逻辑。它强调了直接导出条件语句的挑战,并提供了规避这些挑战的解决方案。

条件逻辑不能导出到 ONNX,除非将其重构为使用 torch.cond()。让我们从一个实现测试的简单模型开始。

你将学到什么

  • 如何重构模型,使其使用 torch.cond() 以便导出。

  • 如何将带有控制流逻辑的模型导出到 ONNX。

  • 如何使用 ONNX 优化器优化导出的模型。

先决条件

  • torch >= 2.6

import torch

定义模型

定义了两个模型

ForwardWithControlFlowTest:一个包含 if-else 条件的 forward 方法的模型。

ModelWithControlFlowTest:一个将 ForwardWithControlFlowTest 作为简单 MLP 一部分纳入的模型。使用随机输入张量对模型进行测试,以确认其按预期执行。

class ForwardWithControlFlowTest(torch.nn.Module):
    def forward(self, x):
        if x.sum():
            return x * 2
        return -x


class ModelWithControlFlowTest(torch.nn.Module):
    def __init__(self):
        super().__init__()
        self.mlp = torch.nn.Sequential(
            torch.nn.Linear(3, 2),
            torch.nn.Linear(2, 1),
            ForwardWithControlFlowTest(),
        )

    def forward(self, x):
        out = self.mlp(x)
        return out


model = ModelWithControlFlowTest()

导出模型:首次尝试

使用 torch.export.export 导出此模型会失败,因为 forward 传递中的控制流逻辑会创建一个导出器无法处理的图断裂。这种行为是预期的,因为未使用 torch.cond() 编写的条件逻辑不受支持。

使用 try-except 块来捕获导出过程中预期的失败。如果导出意外成功,则会引发 AssertionError

x = torch.randn(3)
model(x)

try:
    torch.export.export(model, (x,), strict=False)
    raise AssertionError("This export should failed unless PyTorch now supports this model.")
except Exception as e:
    print(e)
def forward(self, arg0_1: "f32[2, 3]", arg1_1: "f32[2]", arg2_1: "f32[1, 2]", arg3_1: "f32[1]", arg4_1: "f32[3]"):
     # File: /var/lib/ci-user/.local/lib/python3.10/site-packages/torch/nn/modules/linear.py:125 in forward, code: return F.linear(input, self.weight, self.bias)
    linear: "f32[2]" = torch.ops.aten.linear.default(arg4_1, arg0_1, arg1_1);  arg4_1 = arg0_1 = arg1_1 = None
    linear_1: "f32[1]" = torch.ops.aten.linear.default(linear, arg2_1, arg3_1);  linear = arg2_1 = arg3_1 = None

     # File: /var/lib/workspace/beginner_source/onnx/export_control_flow_model_to_onnx_tutorial.py:56 in forward, code: if x.sum():
    sum_1: "f32[]" = torch.ops.aten.sum.default(linear_1);  linear_1 = None
    ne: "b8[]" = torch.ops.aten.ne.Scalar(sum_1, 0);  sum_1 = None
    item: "Sym(Eq(u0, 1))" = torch.ops.aten.item.default(ne);  ne = item = None

Could not guard on data-dependent expression Eq(u0, 1) (unhinted: Eq(u0, 1)).  (Size-like symbols: none)

Caused by: (_export/non_strict_utils.py:683 in __torch_function__)
For more information, run with TORCH_LOGS="dynamic"
For extended logs when we create symbols, also add TORCHDYNAMO_EXTENDED_DEBUG_CREATE_SYMBOL="u0"
If you suspect the guard was triggered from C++, add TORCHDYNAMO_EXTENDED_DEBUG_CPP=1
For more debugging help, see https://docs.google.com/document/d/1HSuTTVvYH1pTew89Rtpeu84Ht3nQEFTYhAX3Ypa_xJs/edit?usp=sharing

For C++ stack trace, run with TORCHDYNAMO_EXTENDED_DEBUG_CPP=1

The following call raised this error:
  File "/var/lib/workspace/beginner_source/onnx/export_control_flow_model_to_onnx_tutorial.py", line 56, in forward
    if x.sum():

使用 JIT Tracing 导出 torch.onnx.export()

当使用带有 dynamo=True 参数的 torch.onnx.export() 导出模型时,导出器默认使用 JIT Tracing。这种回退允许模型导出,但由于 Tracing 的限制,生成的 ONNX 图可能无法忠实地表示原始模型逻辑。

onnx_program = torch.onnx.export(model, (x,), dynamo=True)
print(onnx_program.model)
/usr/local/lib/python3.10/dist-packages/onnxscript/converter.py:823: FutureWarning:

'onnxscript.values.Op.param_schemas' is deprecated in version 0.1 and will be removed in the future. Please use '.op_signature' instead.

/usr/local/lib/python3.10/dist-packages/onnxscript/converter.py:823: FutureWarning:

'onnxscript.values.OnnxFunction.param_schemas' is deprecated in version 0.1 and will be removed in the future. Please use '.op_signature' instead.

[torch.onnx] Obtain model graph for `ModelWithControlFlowTest([...]` with `torch.export.export(..., strict=False)`...




def forward(self, arg0_1: "f32[2, 3]", arg1_1: "f32[2]", arg2_1: "f32[1, 2]", arg3_1: "f32[1]", arg4_1: "f32[3]"):
     # File: /var/lib/ci-user/.local/lib/python3.10/site-packages/torch/nn/modules/linear.py:125 in forward, code: return F.linear(input, self.weight, self.bias)
    linear: "f32[2]" = torch.ops.aten.linear.default(arg4_1, arg0_1, arg1_1);  arg4_1 = arg0_1 = arg1_1 = None
    linear_1: "f32[1]" = torch.ops.aten.linear.default(linear, arg2_1, arg3_1);  linear = arg2_1 = arg3_1 = None

     # File: /var/lib/workspace/beginner_source/onnx/export_control_flow_model_to_onnx_tutorial.py:56 in forward, code: if x.sum():
    sum_1: "f32[]" = torch.ops.aten.sum.default(linear_1);  linear_1 = None
    ne: "b8[]" = torch.ops.aten.ne.Scalar(sum_1, 0);  sum_1 = None
    item: "Sym(Eq(u0, 1))" = torch.ops.aten.item.default(ne);  ne = item = None

[torch.onnx] Obtain model graph for `ModelWithControlFlowTest([...]` with `torch.export.export(..., strict=False)`... ❌
[torch.onnx] Obtain model graph for `ModelWithControlFlowTest([...]` with `torch.export.export`...

class GraphModule(torch.nn.Module):
    def forward(self, L_x_: "f32[3][1]cpu"):
        l_x_ = L_x_

         # File: /var/lib/workspace/beginner_source/onnx/export_control_flow_model_to_onnx_tutorial.py:71 in forward, code: out = self.mlp(x)
        l__self___mlp_0: "f32[2][1]cpu" = self.L__self___mlp_0(l_x_);  l_x_ = None
        l__self___mlp_1: "f32[1][1]cpu" = self.L__self___mlp_1(l__self___mlp_0);  l__self___mlp_0 = None

         # File: /var/lib/workspace/beginner_source/onnx/export_control_flow_model_to_onnx_tutorial.py:56 in forward, code: if x.sum():
        sum_1: "f32[][]cpu" = l__self___mlp_1.sum();  l__self___mlp_1 = sum_1 = None


class GraphModule(torch.nn.Module):
    def forward(self, L_x_: "f32[3][1]cpu"):
        l_x_ = L_x_

         # File: /var/lib/workspace/beginner_source/onnx/export_control_flow_model_to_onnx_tutorial.py:71 in forward, code: out = self.mlp(x)
        l__self___mlp_0: "f32[2][1]cpu" = self.L__self___mlp_0(l_x_);  l_x_ = None
        l__self___mlp_1: "f32[1][1]cpu" = self.L__self___mlp_1(l__self___mlp_0);  l__self___mlp_0 = None

         # File: /var/lib/workspace/beginner_source/onnx/export_control_flow_model_to_onnx_tutorial.py:56 in forward, code: if x.sum():
        sum_1: "f32[][]cpu" = l__self___mlp_1.sum();  l__self___mlp_1 = sum_1 = None


class GraphModule(torch.nn.Module):
    def forward(self, L_x_: "f32[3][1]cpu"):
        l_x_ = L_x_

         # File: /var/lib/workspace/beginner_source/onnx/export_control_flow_model_to_onnx_tutorial.py:71 in forward, code: out = self.mlp(x)
        l__self___mlp_0: "f32[2][1]cpu" = self.L__self___mlp_0(l_x_);  l_x_ = None
        l__self___mlp_1: "f32[1][1]cpu" = self.L__self___mlp_1(l__self___mlp_0);  l__self___mlp_0 = None

         # File: /var/lib/workspace/beginner_source/onnx/export_control_flow_model_to_onnx_tutorial.py:56 in forward, code: if x.sum():
        sum_1: "f32[][]cpu" = l__self___mlp_1.sum();  l__self___mlp_1 = sum_1 = None

[torch.onnx] Obtain model graph for `ModelWithControlFlowTest([...]` with `torch.export.export`... ❌
[torch.onnx] Obtain model graph for `ModelWithControlFlowTest([...]` with Torch Script...
/var/lib/workspace/beginner_source/onnx/export_control_flow_model_to_onnx_tutorial.py:56: TracerWarning:

Converting a tensor to a Python boolean might cause the trace to be incorrect. We can't record the data flow of Python values, so this value will be treated as a constant in the future. This means that the trace might not generalize to other inputs!

[torch.onnx] Obtain model graph for `ModelWithControlFlowTest([...]` with Torch Script... ✅
[torch.onnx] Run decomposition...
/var/lib/ci-user/.local/lib/python3.10/site-packages/torch/export/_unlift.py:81: UserWarning:

Attempted to insert a get_attr Node with no underlying reference in the owning GraphModule! Call GraphModule.add_submodule to add the necessary submodule, GraphModule.add_parameter to add the necessary Parameter, or nn.Module.register_buffer to add the necessary buffer

/var/lib/ci-user/.local/lib/python3.10/site-packages/torch/fx/graph.py:1772: UserWarning:

Node lifted_tensor_6 target lifted_tensor_6 lifted_tensor_6 of  does not reference an nn.Module, nn.Parameter, or buffer, which is what 'get_attr' Nodes typically target

[torch.onnx] Run decomposition... ✅
[torch.onnx] Translate the graph into ONNX...
[torch.onnx] Translate the graph into ONNX... ✅
<
    ir_version=10,
    opset_imports={'pkg.onnxscript.torch_lib.common': 1, '': 18},
    producer_name='pytorch',
    producer_version='2.7.0+cu126',
    domain=None,
    model_version=None,
>
graph(
    name=main_graph,
    inputs=(
        %"input_1"<FLOAT,[3]>
    ),
    outputs=(
        %"mul"<FLOAT,[1]>
    ),
    initializers=(
        %"model.mlp.0.bias"<FLOAT,[2]>,
        %"model.mlp.1.bias"<FLOAT,[1]>
    ),
) {
    0 |  # node_Constant_8
         %"val_0"<FLOAT,[3,2]> ⬅️ ::Constant() {value=Tensor<FLOAT,[3,2]>(array([[ 0.44140652,  0.53036046],
                [ 0.47920528, -0.1264995 ],
                [-0.13525727,  0.11650391]], dtype=float32), name='val_0')}
    1 |  # node_MatMul_1
         %"val_1"<FLOAT,[2]> ⬅️ ::MatMul(%"input_1", %"val_0")
    2 |  # node_Add_2
         %"linear"<FLOAT,[2]> ⬅️ ::Add(%"val_1", %"model.mlp.0.bias")
    3 |  # node_Constant_9
         %"val_2"<FLOAT,[2,1]> ⬅️ ::Constant() {value=Tensor<FLOAT,[2,1]>(array([[ 0.62334496],
                [-0.5187534 ]], dtype=float32), name='val_2')}
    4 |  # node_MatMul_4
         %"val_3"<FLOAT,[1]> ⬅️ ::MatMul(%"linear", %"val_2")
    5 |  # node_Add_5
         %"linear_1"<FLOAT,[1]> ⬅️ ::Add(%"val_3", %"model.mlp.1.bias")
    6 |  # node_Constant_10
         %"convert_element_type_default"<FLOAT,[]> ⬅️ ::Constant() {value=Tensor<FLOAT,[]>(array(2., dtype=float32), name='convert_element_type_default')}
    7 |  # node_Mul_7
         %"mul"<FLOAT,[1]> ⬅️ ::Mul(%"linear_1", %"convert_element_type_default")
    return %"mul"<FLOAT,[1]>
}

建议的补丁:使用 torch.cond() 进行重构

为了使控制流可导出,本教程演示了如何将 ForwardWithControlFlowTest 中的 forward 方法替换为使用 torch.cond`() 重构的版本。

重构细节

两个辅助函数 (identity2 和 neg) 代表条件逻辑的分支:* 使用 torch.cond`() 指定条件和两个分支以及输入参数。* 然后将更新后的 forward 方法动态分配给模型中的 ForwardWithControlFlowTest 实例。打印子模块列表以确认替换。

def new_forward(x):
    def identity2(x):
        return x * 2

    def neg(x):
        return -x

    return torch.cond(x.sum() > 0, identity2, neg, (x,))


print("the list of submodules")
for name, mod in model.named_modules():
    print(name, type(mod))
    if isinstance(mod, ForwardWithControlFlowTest):
        mod.forward = new_forward
the list of submodules
 <class '__main__.ModelWithControlFlowTest'>
mlp <class 'torch.nn.modules.container.Sequential'>
mlp.0 <class 'torch.nn.modules.linear.Linear'>
mlp.1 <class 'torch.nn.modules.linear.Linear'>
mlp.2 <class '__main__.ForwardWithControlFlowTest'>

让我们看看 FX 图是什么样的。

print(torch.export.export(model, (x,), strict=False))
ExportedProgram:
    class GraphModule(torch.nn.Module):
        def forward(self, p_mlp_0_weight: "f32[2, 3]", p_mlp_0_bias: "f32[2]", p_mlp_1_weight: "f32[1, 2]", p_mlp_1_bias: "f32[1]", x: "f32[3]"):
             # File: /var/lib/ci-user/.local/lib/python3.10/site-packages/torch/nn/modules/linear.py:125 in forward, code: return F.linear(input, self.weight, self.bias)
            linear: "f32[2]" = torch.ops.aten.linear.default(x, p_mlp_0_weight, p_mlp_0_bias);  x = p_mlp_0_weight = p_mlp_0_bias = None
            linear_1: "f32[1]" = torch.ops.aten.linear.default(linear, p_mlp_1_weight, p_mlp_1_bias);  linear = p_mlp_1_weight = p_mlp_1_bias = None

             # File: /var/lib/ci-user/.local/lib/python3.10/site-packages/torch/nn/modules/container.py:240 in forward, code: input = module(input)
            sum_1: "f32[]" = torch.ops.aten.sum.default(linear_1)
            gt: "b8[]" = torch.ops.aten.gt.Scalar(sum_1, 0);  sum_1 = None

             # File: <eval_with_key>.30:9 in forward, code: cond = torch.ops.higher_order.cond(l_args_0_, cond_true_0, cond_false_0, [l_args_3_0_]);  l_args_0_ = cond_true_0 = cond_false_0 = l_args_3_0_ = None
            true_graph_0 = self.true_graph_0
            false_graph_0 = self.false_graph_0
            cond = torch.ops.higher_order.cond(gt, true_graph_0, false_graph_0, [linear_1]);  gt = true_graph_0 = false_graph_0 = linear_1 = None
            getitem: "f32[1]" = cond[0];  cond = None
            return (getitem,)

        class true_graph_0(torch.nn.Module):
            def forward(self, linear_1: "f32[1]"):
                 # File: <eval_with_key>.25:6 in forward, code: mul = l_args_3_0__1.mul(2);  l_args_3_0__1 = None
                mul: "f32[1]" = torch.ops.aten.mul.Tensor(linear_1, 2);  linear_1 = None
                return (mul,)

        class false_graph_0(torch.nn.Module):
            def forward(self, linear_1: "f32[1]"):
                 # File: <eval_with_key>.26:6 in forward, code: neg = l_args_3_0__1.neg();  l_args_3_0__1 = None
                neg: "f32[1]" = torch.ops.aten.neg.default(linear_1);  linear_1 = None
                return (neg,)

Graph signature: ExportGraphSignature(input_specs=[InputSpec(kind=<InputKind.PARAMETER: 2>, arg=TensorArgument(name='p_mlp_0_weight'), target='mlp.0.weight', persistent=None), InputSpec(kind=<InputKind.PARAMETER: 2>, arg=TensorArgument(name='p_mlp_0_bias'), target='mlp.0.bias', persistent=None), InputSpec(kind=<InputKind.PARAMETER: 2>, arg=TensorArgument(name='p_mlp_1_weight'), target='mlp.1.weight', persistent=None), InputSpec(kind=<InputKind.PARAMETER: 2>, arg=TensorArgument(name='p_mlp_1_bias'), target='mlp.1.bias', persistent=None), 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='getitem'), target=None)])
Range constraints: {}

让我们再次导出。

onnx_program = torch.onnx.export(model, (x,), dynamo=True)
print(onnx_program.model)
[torch.onnx] Obtain model graph for `ModelWithControlFlowTest([...]` with `torch.export.export(..., strict=False)`...
[torch.onnx] Obtain model graph for `ModelWithControlFlowTest([...]` with `torch.export.export(..., strict=False)`... ✅
[torch.onnx] Run decomposition...
[torch.onnx] Run decomposition... ✅
[torch.onnx] Translate the graph into ONNX...
[torch.onnx] Translate the graph into ONNX... ✅
<
    ir_version=10,
    opset_imports={'pkg.onnxscript.torch_lib.common': 1, '': 18, 'pkg.torch.__subgraph__': 1},
    producer_name='pytorch',
    producer_version='2.7.0+cu126',
    domain=None,
    model_version=None,
>
graph(
    name=main_graph,
    inputs=(
        %"x"<FLOAT,[3]>
    ),
    outputs=(
        %"getitem"<FLOAT,[1]>
    ),
    initializers=(
        %"mlp.0.bias"<FLOAT,[2]>,
        %"mlp.1.bias"<FLOAT,[1]>
    ),
) {
     0 |  # node_Constant_11
          %"val_0"<FLOAT,[3,2]> ⬅️ ::Constant() {value=Tensor<FLOAT,[3,2]>(array([[ 0.44140652,  0.53036046],
                 [ 0.47920528, -0.1264995 ],
                 [-0.13525727,  0.11650391]], dtype=float32), name='val_0')}
     1 |  # node_MatMul_1
          %"val_1"<FLOAT,[2]> ⬅️ ::MatMul(%"x", %"val_0")
     2 |  # node_Add_2
          %"linear"<FLOAT,[2]> ⬅️ ::Add(%"val_1", %"mlp.0.bias")
     3 |  # node_Constant_12
          %"val_2"<FLOAT,[2,1]> ⬅️ ::Constant() {value=Tensor<FLOAT,[2,1]>(array([[ 0.62334496],
                 [-0.5187534 ]], dtype=float32), name='val_2')}
     4 |  # node_MatMul_4
          %"val_3"<FLOAT,[1]> ⬅️ ::MatMul(%"linear", %"val_2")
     5 |  # node_Add_5
          %"linear_1"<FLOAT,[1]> ⬅️ ::Add(%"val_3", %"mlp.1.bias")
     6 |  # node_ReduceSum_6
          %"sum_1"<FLOAT,[]> ⬅️ ::ReduceSum(%"linear_1") {keepdims=False, noop_with_empty_axes=0}
     7 |  # node_Constant_13
          %"scalar_tensor_default"<FLOAT,[]> ⬅️ ::Constant() {value=Tensor<FLOAT,[]>(array(0., dtype=float32), name='scalar_tensor_default')}
     8 |  # node_Greater_9
          %"gt"<BOOL,[]> ⬅️ ::Greater(%"sum_1", %"scalar_tensor_default")
     9 |  # node_If_10
          %"getitem"<FLOAT,[1]> ⬅️ ::If(%"gt") {then_branch=
              graph(
                  name=true_graph_0,
                  inputs=(

                  ),
                  outputs=(
                      %"mul_true_graph_0"<FLOAT,[1]>
                  ),
              ) {
                  0 |  # node_Constant_1
                       %"scalar_tensor_default_2"<FLOAT,[]> ⬅️ ::Constant() {value=Tensor<FLOAT,[]>(array(2., dtype=float32), name='scalar_tensor_default_2')}
                  1 |  # node_Mul_2
                       %"mul_true_graph_0"<FLOAT,[1]> ⬅️ ::Mul(%"linear_1", %"scalar_tensor_default_2")
                  return %"mul_true_graph_0"<FLOAT,[1]>
              }, else_branch=
              graph(
                  name=false_graph_0,
                  inputs=(

                  ),
                  outputs=(
                      %"neg_false_graph_0"<FLOAT,[1]>
                  ),
              ) {
                  0 |  # node_Neg_0
                       %"neg_false_graph_0"<FLOAT,[1]> ⬅️ ::Neg(%"linear_1")
                  return %"neg_false_graph_0"<FLOAT,[1]>
              }}
    return %"getitem"<FLOAT,[1]>
}

我们可以优化模型,并去掉为捕获控制流分支而创建的模型本地函数。

<
    ir_version=10,
    opset_imports={'pkg.onnxscript.torch_lib.common': 1, '': 18, 'pkg.torch.__subgraph__': 1},
    producer_name='pytorch',
    producer_version='2.7.0+cu126',
    domain=None,
    model_version=None,
>
graph(
    name=main_graph,
    inputs=(
        %"x"<FLOAT,[3]>
    ),
    outputs=(
        %"getitem"<FLOAT,[1]>
    ),
    initializers=(
        %"mlp.0.bias"<FLOAT,[2]>,
        %"mlp.1.bias"<FLOAT,[1]>
    ),
) {
     0 |  # node_Constant_11
          %"val_0"<FLOAT,[3,2]> ⬅️ ::Constant() {value=Tensor<FLOAT,[3,2]>(array([[ 0.44140652,  0.53036046],
                 [ 0.47920528, -0.1264995 ],
                 [-0.13525727,  0.11650391]], dtype=float32), name='val_0')}
     1 |  # node_MatMul_1
          %"val_1"<FLOAT,[2]> ⬅️ ::MatMul(%"x", %"val_0")
     2 |  # node_Add_2
          %"linear"<FLOAT,[2]> ⬅️ ::Add(%"val_1", %"mlp.0.bias")
     3 |  # node_Constant_12
          %"val_2"<FLOAT,[2,1]> ⬅️ ::Constant() {value=Tensor<FLOAT,[2,1]>(array([[ 0.62334496],
                 [-0.5187534 ]], dtype=float32), name='val_2')}
     4 |  # node_MatMul_4
          %"val_3"<FLOAT,[1]> ⬅️ ::MatMul(%"linear", %"val_2")
     5 |  # node_Add_5
          %"linear_1"<FLOAT,[1]> ⬅️ ::Add(%"val_3", %"mlp.1.bias")
     6 |  # node_ReduceSum_6
          %"sum_1"<FLOAT,[]> ⬅️ ::ReduceSum(%"linear_1") {keepdims=False, noop_with_empty_axes=0}
     7 |  # node_Constant_13
          %"scalar_tensor_default"<FLOAT,[]> ⬅️ ::Constant() {value=Tensor<FLOAT,[]>(array(0., dtype=float32), name='scalar_tensor_default')}
     8 |  # node_Greater_9
          %"gt"<BOOL,[]> ⬅️ ::Greater(%"sum_1", %"scalar_tensor_default")
     9 |  # node_If_10
          %"getitem"<FLOAT,[1]> ⬅️ ::If(%"gt") {then_branch=
              graph(
                  name=true_graph_0,
                  inputs=(

                  ),
                  outputs=(
                      %"mul_true_graph_0"<FLOAT,[1]>
                  ),
              ) {
                  0 |  # node_Constant_1
                       %"scalar_tensor_default_2"<FLOAT,[]> ⬅️ ::Constant() {value=Tensor<FLOAT,[]>(array(2., dtype=float32), name='scalar_tensor_default_2')}
                  1 |  # node_Mul_2
                       %"mul_true_graph_0"<FLOAT,[1]> ⬅️ ::Mul(%"linear_1", %"scalar_tensor_default_2")
                  return %"mul_true_graph_0"<FLOAT,[1]>
              }, else_branch=
              graph(
                  name=false_graph_0,
                  inputs=(

                  ),
                  outputs=(
                      %"neg_false_graph_0"<FLOAT,[1]>
                  ),
              ) {
                  0 |  # node_Neg_0
                       %"neg_false_graph_0"<FLOAT,[1]> ⬅️ ::Neg(%"linear_1")
                  return %"neg_false_graph_0"<FLOAT,[1]>
              }}
    return %"getitem"<FLOAT,[1]>
}

结论

本教程演示了将带有条件逻辑的模型导出到 ONNX 的挑战,并提供了一个使用 torch.cond() 的实用解决方案。尽管默认导出器可能会失败或生成不完美的图,但重构模型的逻辑可以确保兼容性并生成忠实的 ONNX 表示。

通过理解这些技术,我们可以克服在 PyTorch 模型中处理控制流时常见的陷阱,并确保与 ONNX 工作流程的顺利集成。

延伸阅读

下面的列表引用了一些教程,它们涵盖了从基本示例到高级场景,顺序不一定按列表排列。您可以随意直接跳到您感兴趣的特定主题,或者耐心地通读所有教程,了解 ONNX 导出器的所有内容。

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