[Eager] clear_gradient use set_constant but not zeros_like (#43171)

* clear_gradient use set_constant but not zeros_like

paddle/fluid/pybind/eager_method.cc

@@ -53,6 +53,7 @@ typedef SSIZE_T ssize_t;
 #include "paddle/fluid/memory/allocation/mmap_allocator.h"
 #include "paddle/fluid/pybind/tensor_py.h"
 #include "paddle/phi/core/ddim.h"
+#include "paddle/phi/kernels/funcs/math_function.h"
 
 namespace paddle {
 namespace pybind {
@@ -518,7 +519,10 @@ static PyObject* tensor_clear_gradient(TensorObject* self, PyObject* args,
     } else if (grad->is_dense_tensor()) {
       if (grad->initialized()) {
         if (set_to_zero) {
-          grad->set_impl(paddle::experimental::zeros_like(*grad).impl());
+          auto* grad_t = static_cast<phi::DenseTensor*>(grad->impl().get());
+          auto* dev_ctx =
+              platform::DeviceContextPool::Instance().Get(grad_t->place());
+          phi::funcs::set_constant(*dev_ctx, grad_t, 0.0);
           if (is_leaf) {
             std::static_pointer_cast<egr::GradNodeAccumulation>(
                 egr::EagerUtils::grad_node(self->tensor))
@@ -555,15 +559,28 @@ static PyObject* tensor__zero_grads(TensorObject* self, PyObject* args,
                        "Please check if you have manually cleared"
                        "the grad inside autograd_meta"));
     if (grad->initialized()) {
+      if (grad->is_dense_tensor()) {
+        auto* t = static_cast<phi::DenseTensor*>(grad->impl().get());
+        auto* dev_ctx = platform::DeviceContextPool::Instance().Get(t->place());
+        phi::funcs::set_constant(*dev_ctx, t, 0.0);
+      } else {
         grad->set_impl(paddle::experimental::zeros_like(*(grad)).impl());
       }
+    }
   } else {
     auto meta = egr::EagerUtils::unsafe_autograd_meta(self->tensor);
     if (meta->MutableGrad()->initialized()) {
+      if (meta->MutableGrad()->is_dense_tensor()) {
+        auto* t =
+            static_cast<phi::DenseTensor*>(meta->MutableGrad()->impl().get());
+        auto* dev_ctx = platform::DeviceContextPool::Instance().Get(t->place());
+        phi::funcs::set_constant(*dev_ctx, t, 0.0);
+      } else {
         meta->MutableGrad()->set_impl(
             paddle::experimental::zeros_like(*(meta->MutableGrad())).impl());
       }
     }
+  }
 
   RETURN_PY_NONE