[Fix] Fix cos double grad functor

paddle/phi/kernels/funcs/activation_functor.h

@@ -398,7 +398,7 @@ struct CosDoubleGradFunctor : public BaseActivationFunctor<T> {
                   const DenseTensor* ddX,
                   DenseTensor* dX,
                   DenseTensor* ddOut) const {
-    auto* d = dev.eigen_device();
+    auto* device = dev.eigen_device();
     auto d2d1x = EigenVector<T>::Flatten(
         GET_DATA_SAFELY(ddX, "Input", "d2d1x", "CosDoubleGrad"));
     auto x = EigenVector<T>::Flatten(
@@ -407,21 +407,17 @@ struct CosDoubleGradFunctor : public BaseActivationFunctor<T> {
     // calculate d2x first, so d2d1y can inplace d2d1x
     auto d2x = EigenVector<T>::Flatten(
         GET_DATA_SAFELY(dX, "Output", "d2x", "CosDoubleGrad"));
-    if (ddOut) {
-      if (dOut) {
-        auto d1y = EigenVector<T>::Flatten(
-            GET_DATA_SAFELY(dOut, "Output", "d1y", "CosDoubleGrad"));
-        d2x.device(*d) = -d2d1x * x.unaryExpr(Cosine<T>()) * d1y;
-      } else {
-        d2x.device(*d) = x * static_cast<T>(0);
-      }
+    if (dX) {
+      auto d1y = EigenVector<T>::Flatten(
+          GET_DATA_SAFELY(dOut, "Output", "d1y", "CosDoubleGrad"));
+      d2x.device(*device) = -d2d1x * x.unaryExpr(Cosine<T>()) * d1y;
     }
 
-    if (dX) {
+    if (ddOut) {
       // calculate d2d1y
       auto d2d1y = EigenVector<T>::Flatten(
           GET_DATA_SAFELY(ddOut, "Output", "d2d1y", "CosDoubleGrad"));
-      d2d1y.device(*d) = -d2d1x * x.unaryExpr(Sine<T>());
+      d2d1y.device(*device) = -d2d1x * x.unaryExpr(Sine<T>());
     }
   }
   static constexpr ActBwdOpFwdDeps FwdDeps() { return kDepX; }

test/legacy_test/test_activation_nn_grad.py

@@ -17,6 +17,7 @@
 import gradient_checker
 import numpy as np
 from decorator_helper import prog_scope
+from utils import dygraph_guard, static_guard
 
 import paddle
 import paddle.nn.functional as F
@@ -544,6 +545,52 @@ def test_grad(self):
             self.func(p)
 
 
+class TestCosDoubleGradCheck2(unittest.TestCase):
+    @test_with_pir_api
+    def _check_cos_double_dynamic(self, place):
+        with dygraph_guard():
+            x = paddle.randn([64, 64])
+            x = paddle.to_tensor(x, place=place, stop_gradient=False)
+            y = paddle.cos(x)
+            dx = paddle.grad(y, x, create_graph=True)
+            dxx_result = paddle.grad(dx, x)[0]
+            dxx_expected = -paddle.cos(x)
+            np.testing.assert_allclose(
+                dxx_result.numpy(),
+                dxx_expected.numpy(),
+                1e-6,
+                1e-6,
+            )
+
+    @test_with_pir_api
+    def _check_cos_double_static(self, place):
+        x_data = np.random.randn(64, 64).astype("float32")
+        with static_guard():
+            main_prog = paddle.static.Program()
+            starup_prog = paddle.static.Program()
+            with paddle.static.program_guard(main_prog, starup_prog):
+                x = paddle.assign(x_data)
+                x.stop_gradient = False
+                y = paddle.cos(x)
+                dx = paddle.static.gradients(y, x)
+                dxx = paddle.static.gradients(dx, x)[0]
+
+            exe = paddle.static.Executor(place)
+            exe.run(starup_prog)
+            (dxx_result,) = exe.run(main_prog, fetch_list=[dxx])
+            dxx_expected = -np.cos(x_data)
+            np.testing.assert_allclose(dxx_result, dxx_expected, 1e-6, 1e-6)
+
+    def test_cos_double_grad(self):
+        places = [base.CPUPlace()]
+        if core.is_compiled_with_cuda():
+            places.append(base.CUDAPlace(0))
+
+        for place in places:
+            self._check_cos_double_dynamic(place)
+            self._check_cos_double_static(place)
+
+
 class TestPowDoubleGradCheck1(unittest.TestCase):
     def pow_wrapper(self, x):
         return paddle.pow(x[0], 2)