add SetConstant method in math_function.h

paddle/operators/math/CMakeLists.txt

 if(WITH_GPU)
     nv_library(math_function SRCS math_function.cc math_function.cu im2col.cc
       im2col.cu DEPS cblas device_context operator)
+    nv_test(math_function_test SRCS math_function_test.cc DEPS math_function tensor)
     nv_library(softmax_function SRCS softmax.cc softmax.cu
       DEPS operator)
     nv_library(cross_entropy_function SRCS cross_entropy.cc cross_entropy.cu
@@ -8,9 +9,9 @@ if(WITH_GPU)
 else()
     cc_library(math_function SRCS math_function.cc im2col.cc
       DEPS cblas device_context operator)
+    cc_test(math_function_test SRCS math_function_test.cc DEPS math_function tensor)
     cc_library(softmax_function SRCS softmax.cc DEPS operator)
     cc_library(cross_entropy_function SRCS cross_entropy.cc DEPS operator)
 endif()
 
-nv_test(math_function_test SRCS math_function_test.cc DEPS math_function tensor)
 cc_test(im2col_test SRCS im2col_test.cc DEPS math_function tensor)

paddle/operators/math/math_function.h

@@ -52,6 +52,7 @@ int LAPACKE_dgetri(int matrix_layout, int n, double* a, int lda,
 
 #include <cmath>
 
+#include "paddle/framework/eigen.h"
 #include "paddle/framework/tensor.h"
 #include "paddle/platform/device_context.h"
 #include "paddle/platform/enforce.h"
@@ -84,6 +85,13 @@ void matmul(const platform::DeviceContext& context,
             const framework::Tensor& matrix_b, bool trans_b, T alpha,
             framework::Tensor* matrix_out, T beta);
 
+template <typename Place, typename T>
+void SetConstant(const platform::DeviceContext& context,
+                 framework::Tensor* tensor, T num) {
+  auto t = framework::EigenVector<T>::Flatten(*tensor);
+  t.device(*context.GetEigenDevice<Place>()) = t.constant(static_cast<T>(num));
+}
+
 }  // namespace math
 }  // namespace operators
 }  // namespace paddle

paddle/operators/math/math_function_test.cc

@@ -243,3 +243,24 @@ TEST(math_function, gemm_trans_clbas) {
   EXPECT_EQ(input3_ptr[6], 86);
   EXPECT_EQ(input3_ptr[7], 99);
 }
+
+TEST(math_function, zero) {
+  paddle::framework::Tensor tensor;
+  auto* cpu_place = new paddle::platform::CPUPlace();
+  float* t = tensor.mutable_data<float>({2, 2}, *cpu_place);
+  paddle::platform::CPUDeviceContext context(*cpu_place);
+  paddle::operators::math::SetConstant<paddle::platform::CPUPlace, float>(
+      context, &tensor, 0);
+  EXPECT_EQ(t[0], 0);
+  EXPECT_EQ(t[1], 0);
+  EXPECT_EQ(t[2], 0);
+  EXPECT_EQ(t[3], 0);
+
+  paddle::operators::math::SetConstant<paddle::platform::CPUPlace, float>(
+      context, &tensor, 1);
+
+  EXPECT_EQ(t[0], 1);
+  EXPECT_EQ(t[1], 1);
+  EXPECT_EQ(t[2], 1);
+  EXPECT_EQ(t[3], 1);
+}