From 40bafbcbf9157d706448121f6b738c1234352c12 Mon Sep 17 00:00:00 2001
From: Liu Yiqun <liuyiqun01@baidu.com>
Date: Wed, 24 Dec 2025 11:47:40 +0800
Subject: [PATCH 1/2] Implement BackwardGraphExtractor for torch.

---
 .../test/backward_graph_extractor_test.sh     |  29 ++++
 .../sample_passes/backward_graph_extractor.py | 148 ++++++++++++++++++
 2 files changed, 177 insertions(+)
 create mode 100644 graph_net/test/backward_graph_extractor_test.sh
 create mode 100644 graph_net/torch/sample_passes/backward_graph_extractor.py

diff --git a/graph_net/test/backward_graph_extractor_test.sh b/graph_net/test/backward_graph_extractor_test.sh
new file mode 100644
index 000000000..3cc260e0d
--- /dev/null
+++ b/graph_net/test/backward_graph_extractor_test.sh
@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+GRAPH_NET_ROOT=$(python -c "import graph_net, os; print(os.path.dirname(os.path.dirname(graph_net.__file__)))")
+MODEL_PATH_PREFIX=$GRAPH_NET_ROOT
+OUTPUT_DIR=/tmp/backward_graph_workspace
+FRAMEWORK="torch"
+HANDLER_CONFIG=$(base64 -w 0 <<EOF
+{
+    "handler_path": "$GRAPH_NET_ROOT/graph_net/torch/sample_passes/backward_graph_extractor.py",
+    "handler_class_name": "BackwardGraphExtractorPass",
+    "handler_config": {
+        "model_path_prefix": "$MODEL_PATH_PREFIX",
+        "output_dir": "$OUTPUT_DIR",
+        "device": "cuda",
+        "resume": false
+    }
+}
+EOF
+)
+
+run_case() {
+    local rel_sample_path="$1"
+    python -m graph_net.model_path_handler \
+        --model-path "$rel_sample_path" \
+        --handler-config "$HANDLER_CONFIG"
+}
+
+run_case "samples/torchvision/resnet18"
+#run_case "samples/transformers-auto-model/albert-base-v2"
\ No newline at end of file
diff --git a/graph_net/torch/sample_passes/backward_graph_extractor.py b/graph_net/torch/sample_passes/backward_graph_extractor.py
new file mode 100644
index 000000000..384403a03
--- /dev/null
+++ b/graph_net/torch/sample_passes/backward_graph_extractor.py
@@ -0,0 +1,148 @@
+import os
+import inspect
+from pathlib import Path
+
+import torch
+from torch._functorch.aot_autograd import aot_module
+
+from graph_net.sample_pass.sample_pass import SamplePass
+from graph_net.sample_pass.resumable_sample_pass_mixin import ResumableSamplePassMixin
+from graph_net.torch.extractor import GraphExtractor as BuiltinGraphExtractor
+from graph_net.torch.fx_graph_module_util import (
+    get_torch_module_and_inputs,
+    _get_tensor_metas,
+)
+
+
+class BackwardGraphExtractor:
+    def __init__(self, model_name, model_path, output_dir, device):
+        self.model_path = model_path
+        self.output_dir = output_dir
+        self.device = device
+        self.builtin_extractor = BuiltinGraphExtractor(
+            name=model_name,
+            dynamic=False,
+            mut_graph_codes=[],
+            placeholder_auto_rename=False,
+            workspace_path=output_dir,
+        )
+
+    def __call__(self):
+        module, example_inputs = get_torch_module_and_inputs(
+            self.model_path, use_dummy_inputs=False, device=self.device
+        )
+        module.train()
+
+        example_inputs = self.set_requires_grad_for_forward_inputs(
+            self.model_path, module, example_inputs
+        )
+        bw_gm, backward_inputs = self.capture_backward_graph(module, example_inputs)
+        print(bw_gm.graph)
+        self.builtin_extractor(bw_gm, backward_inputs)
+
+    def capture_backward_graph(self, module, example_inputs):
+        backward_gm_holder = {}
+        backward_inputs = []
+
+        def forward_compiler(fx_gm, example_inputs):
+            return fx_gm
+
+        def backward_compiler(fx_gm, example_inputs):
+            # Save the backward fx.Graph
+            backward_gm_holder["gm"] = fx_gm
+
+            placeholders = [n for n in fx_gm.graph.nodes if n.op == "placeholder"]
+            origin_forward = fx_gm.forward
+
+            def wrapped_forward(*args):
+                for node, arg in zip(placeholders, args):
+                    if torch.is_tensor(arg):
+                        backward_inputs.append(arg.detach().clone())
+                    else:
+                        print(f"- {node.name} is not a torch.Tensor.")
+                return origin_forward(*args)
+
+            fx_gm.forward = wrapped_forward
+            return fx_gm
+
+        compiled = aot_module(
+            module,
+            fw_compiler=forward_compiler,
+            bw_compiler=backward_compiler,
+        )
+        outs = compiled(*example_inputs)
+        if isinstance(outs, torch.Tensor):
+            outs = [outs]
+
+        outs_grad = [torch.ones_like(out) for out in outs]
+        torch.autograd.backward(outs, outs_grad)
+        return backward_gm_holder["gm"], backward_inputs
+
+    def _requires_grad(self, name, tensor):
+        if not tensor.is_floating_point():
+            return False
+
+        nograd_parameter_keywords = ["running_mean", "running_var"]
+        for keyword in nograd_parameter_keywords:
+            if keyword in name:
+                return False
+
+        return True
+
+    def set_requires_grad_for_forward_inputs(
+        self, model_path, graph_module, example_inputs
+    ):
+        tensor_metas = _get_tensor_metas(model_path)
+        name2tensor_meta = {
+            tensor_meta.name: tensor_meta for tensor_meta in tensor_metas
+        }
+        for input_idx, name in enumerate(
+            inspect.signature(graph_module.forward).parameters
+        ):
+            tensor = example_inputs[input_idx]
+            tensor_meta = name2tensor_meta[name]
+            original_name = (
+                tensor_meta.original_name
+                if hasattr(tensor_meta, "original_name") and tensor_meta.original_name
+                else name
+            )
+            tensor.requires_grad = self._requires_grad(original_name, tensor)
+            # print(f"{name}, {original_name}, requires_grad:{tensor.requires_grad}")
+        return example_inputs
+
+
+class BackwardGraphExtractorPass(SamplePass, ResumableSamplePassMixin):
+    """SamplePass wrapper to generate Torch unittests via model_path_handler."""
+
+    def __init__(self, config=None):
+        super().__init__(config)
+
+    def declare_config(
+        self,
+        model_path_prefix: str,
+        output_dir: str,
+        device: str = "auto",
+        resume: bool = False,
+        limits_handled_models: int = None,
+    ):
+        pass
+
+    def __call__(self, rel_model_path: str):
+        self.resumable_handle_sample(rel_model_path)
+
+    def sample_handled(self, rel_model_path: str) -> bool:
+        return self.naive_sample_handled(rel_model_path, search_file_name="model.py")
+
+    def resume(self, rel_model_path: str):
+        model_path_prefix = Path(self.config["model_path_prefix"])
+        model_name = f"{os.path.basename(rel_model_path)}_backward"
+        model_path = model_path_prefix / rel_model_path
+        output_dir = Path(self.config["output_dir"]) / os.path.dirname(rel_model_path)
+        device = self._choose_device(self.config["device"])
+        extractor = BackwardGraphExtractor(model_name, model_path, output_dir, device)
+        extractor()
+
+    def _choose_device(self, device) -> str:
+        if device in ["cpu", "cuda"]:
+            return device
+        return "cuda" if torch.cuda.is_available() else "cpu"

From de2a081300d3f285d39a08f693cf46e73ac50b4e Mon Sep 17 00:00:00 2001
From: Liu Yiqun <liuyiqun01@baidu.com>
Date: Wed, 24 Dec 2025 13:26:47 +0800
Subject: [PATCH 2/2] Remove None from returns.

---
 .../sample_passes/backward_graph_extractor.py | 25 +++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/graph_net/torch/sample_passes/backward_graph_extractor.py b/graph_net/torch/sample_passes/backward_graph_extractor.py
index 384403a03..1e5c27e99 100644
--- a/graph_net/torch/sample_passes/backward_graph_extractor.py
+++ b/graph_net/torch/sample_passes/backward_graph_extractor.py
@@ -37,7 +37,7 @@ def __call__(self):
             self.model_path, module, example_inputs
         )
         bw_gm, backward_inputs = self.capture_backward_graph(module, example_inputs)
-        print(bw_gm.graph)
+        # print(bw_gm.graph)
         self.builtin_extractor(bw_gm, backward_inputs)
 
     def capture_backward_graph(self, module, example_inputs):
@@ -76,7 +76,28 @@ def wrapped_forward(*args):
 
         outs_grad = [torch.ones_like(out) for out in outs]
         torch.autograd.backward(outs, outs_grad)
-        return backward_gm_holder["gm"], backward_inputs
+        bw_gm = self._remove_none_from_output(backward_gm_holder["gm"])
+        return bw_gm, backward_inputs
+
+    def _remove_none_from_output(self, gm):
+        output_node = next(
+            (n for n in gm.graph.nodes if n.op == "output"),
+            None,
+        )
+        outs = (
+            output_node.args[0]
+            if output_node and isinstance(output_node.args, (tuple, list))
+            else output_node.args
+        )
+        if isinstance(outs, (tuple, list)):
+            new_outs = tuple(out for out in outs if out is not None)
+            if new_outs != outs:
+                output_node.args = (new_outs,)
+
+        gm.graph.eliminate_dead_code()
+        gm.graph.lint()
+        gm.recompile()
+        return gm
 
     def _requires_grad(self, name, tensor):
         if not tensor.is_floating_point():