Use macro to simplify element wise cpu math functions

include/caffe/util/math_functions.hpp

@@ -126,22 +126,33 @@ inline char caffe_sign(Dtype val) {
   return (Dtype(0) < val) - (val < Dtype(0));
 }
 
-template<typename Dtype>
-void caffe_cpu_sign(const int n, const Dtype* x, Dtype* y) {
-  for (int i = 0; i < n; ++i) {
-    y[i] = caffe_sign<Dtype>(x[i]);
+// The following two macros are modifications of DEFINE_VSL_UNARY_FUNC
+//   in include/caffe/util/mkl_alternate.hpp authored by @Rowland Depp.
+// Please refer to commit 7e8ef25c7 of the boost-eigen branch.
+// Git cherry picking that commit caused a conflict hard to resolve and
+//   copying that file in convenient for code reviewing.
+// So they have to be pasted here temporarily.
+#define DEFINE_CAFFE_CPU_UNARY_FUNC(name, operation) \
+  template<typename Dtype> \
+  void caffe_cpu_##name(const int n, const Dtype* x, Dtype* y) { \
+    CHECK_GT(n, 0); CHECK(x); CHECK(y); \
+    for (int i = 0; i < n; ++i) { \
+      operation; \
+    } \
   }
-}
+
+#define INSTANTIATE_CAFFE_CPU_UNARY_FUNC(name) \
+  template <> \
+  void caffe_cpu_##name<float>(const int n, const float* x, float* y); \
+  template <> \
+  void caffe_cpu_##name<double>(const int n, const double* x, double* y)
+
+DEFINE_CAFFE_CPU_UNARY_FUNC(sign, y[i] = caffe_sign<Dtype>(x[i]));
 
 template<typename Dtype>
 void caffe_gpu_sign(const int n, const Dtype* x, Dtype* y);
 
-template <typename Dtype>
-void caffe_cpu_fabs(const int n, const Dtype* x, Dtype* y) {
-  for (int i = 0; i < n; ++i) {
-    y[i] = std::fabs(x[i]);
-  }
-}
+DEFINE_CAFFE_CPU_UNARY_FUNC(fabs, y[i] = std::fabs(x[i]));
 
 template <typename Dtype>
 void caffe_gpu_fabs(const int n, const Dtype* x, Dtype* y);

src/caffe/util/math_functions.cpp

@@ -410,16 +410,7 @@ void caffe_gpu_asum<double>(const int n, const double* x, double* y) {
   CUBLAS_CHECK(cublasDasum(Caffe::cublas_handle(), n, x, 1, y));
 }
 
-template <>
-void caffe_cpu_sign<float>(const int n, const float* x, float* y);
-
-template <>
-void caffe_cpu_sign<double>(const int n, const double* x, double* y);
-
-template <>
-void caffe_cpu_fabs<float>(const int n, const float* x, float* y);
-
-template <>
-void caffe_cpu_fabs<double>(const int n, const double* x, double* y);
+INSTANTIATE_CAFFE_CPU_UNARY_FUNC(sign);
+INSTANTIATE_CAFFE_CPU_UNARY_FUNC(fabs);
 
 }  // namespace caffe