[Dy2St]Support call backward() without params in dy2st (#49812)

* Support call backward() without params in dy2st

paddle/fluid/operators/select_output_op.cc

@@ -95,7 +95,8 @@ class SelectOutputInferShape : public framework::InferShapeBase {
   void operator()(framework::InferShapeContext *context) const override {
     OP_INOUT_CHECK(context->HasInput("X"), "Input", "X", "SelectOutput");
     OP_INOUT_CHECK(context->HasInput("Mask"), "Input", "Mask", "SelectOutput");
-    OP_INOUT_CHECK(context->HasOutputs("Out"), "Output", "Out", "SelectOutput");
+    OP_INOUT_CHECK(
+        context->HasOutputs("Out", true), "Output", "Out", "SelectOutput");
   }
 };
 

paddle/fluid/pybind/eager_legacy_custom_python_api.h

@@ -26,9 +26,9 @@ static PyObject *eager_api_run_program(PyObject *self,
                                        PyObject *kwargs) {
   PyThreadState *tstate = nullptr;
   try {
-    auto X = GetTensorListFromArgs("run_program", "X", args, 0, false);
+    auto X = GetTensorListFromArgs("run_program", "X", args, 0, true);
     auto Params = GetTensorListFromArgs("run_program", "Params", args, 1, true);
-    auto Out = GetTensorPtrListFromArgs("run_program", "Out", args, 2, false);
+    auto Out = GetTensorPtrListFromArgs("run_program", "Out", args, 2, true);
     auto OutScope =
         GetScopePtrListFromArgs("run_program", "OutScope", args, 3, false);
     auto DOut = GetTensorPtrListFromArgs("run_program", "DOut", args, 4, true);

python/paddle/fluid/tests/unittests/dygraph_to_static/test_backward_without_params.py

+# Copyright (c) 2023 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+
+import numpy as np
+
+import paddle
+
+
+class Net(paddle.nn.Layer):
+    def __init__(self):
+        super(Net, self).__init__()
+
+    @paddle.jit.to_static
+    def forward(self, x):
+        out = x + 1
+        return out
+
+
+class TestBackwardWithoutParams(unittest.TestCase):
+    def test_run(self):
+        net = Net()
+
+        x = paddle.ones([2, 2])
+        x.stop_gradient = False
+        out = net(x)
+        loss = paddle.mean(out)
+        loss.backward()
+        np.testing.assert_equal(x.grad.numpy(), np.full(x.shape, 0.25))
+
+
+if __name__ == '__main__':
+    unittest.main()

python/paddle/fluid/tests/unittests/dygraph_to_static/test_for_enumerate.py

@@ -377,6 +377,7 @@ class TestTransform(TestTransformBase):
         if not isinstance(dy_outs, (tuple, list)):
             dy_outs = (dy_outs,)
 
+        self.dygraph_func.eval()
         st_outs = self.get_static_output()
         if not isinstance(st_outs, (tuple, list)):
             st_outs = (st_outs,)

python/paddle/jit/dy2static/partial_program.py

@@ -206,10 +206,6 @@ class PartialProgramLayer:
         else:
             return core.Scope()
 
-    @LazyInitialized
-    def __fake_vars(self):
-        return _create_fake_var()
-
     @LazyInitialized
     def _double_grads(self):
         return self._get_double_grads(self._origin_main_program)
@@ -604,7 +600,7 @@ class PartialProgramLayer:
             if isinstance(out, framework.Variable):
                 targets.append(program.global_block().var(out.name))
 
-        if targets and self._params:
+        if targets:
             backward.gradients(targets=targets, inputs=[])
 
         start_idx = len(main_program.block(0).ops) + 2 * len(
@@ -1123,12 +1119,7 @@ class PartialProgramLayer:
                         )
 
     def _valid_vars(self, vars):
-        """
-        Note: run_program_op.InferShape requires `X`/'Out' not be null.
-        But it's common in dy2static, fake varBase is created to handle the
-        problem.
-        """
-        return vars if vars else self.__fake_vars
+        return vars if vars else None
 
 
 def _create_fake_var():