Replace GRU RowWiseAdd Eigen with c implementation (#2712)

* replace gru RowWiseAdd Eigen with c implementation
test=develop

lite/backends/x86/math/math_function.cc

@@ -110,11 +110,11 @@ void set_constant(const lite::Context<Target>& context,
                   lite::Tensor* tensor,
                   float value) {
   TensorSetConstantWithTarget<Target> func(context, tensor, value);
-  //#ifdef PADDLE_WITH_CUDA
+  // #ifdef PADDLE_WITH_CUDA
   // tensor->target().apply_visitor(func);
-  //#else
+  // #else
   func();
-  //#endif
+  // #endif
 }
 
 template <typename T>
@@ -128,12 +128,14 @@ struct RowwiseAdd<lite::TargetType::kX86, T> {
     PADDLE_ENFORCE_EQ(vector.numel(), size);
     PADDLE_ENFORCE_EQ(output->dims(), in_dims);
 
-    auto in = lite::fluid::EigenMatrix<T>::From(input);
-    auto vec = lite::fluid::EigenVector<T>::Flatten(vector);
-    auto out = lite::fluid::EigenMatrix<T>::From(*output);
-
+    const T* input_data = input.data<T>();
+    const T* vector_data = vector.data<T>();
+    T* output_data = output->mutable_data<T>();
     for (int64_t i = 0; i < in_dims[0]; ++i) {
-      out.chip(i, 0) = in.chip(i, 0) + vec;
+      for (int64_t j = 0; j < size; ++j) {
+        output_data[i * in_dims[0] + j] =
+            input_data[i * in_dims[0] + j] + vector_data[j];
+      }
     }
   }
 };