delete Bits.h and move its func into utils/Util.h

Change-Id: Ib7f7d3c65c9850b8420f9a4799835a7ea03572bd

doc/source/math/utils/utils.rst

 Utils
 =======
 
-Bits
--------
-.. doxygenfile:: paddle/math/Bits.h
-
 Memory Handle
 --------------
 .. doxygenfile:: paddle/math/MemoryHandle.h

paddle/gserver/layers/HierarchicalSigmoidLayer.cpp

@@ -14,8 +14,7 @@ limitations under the License. */
 
 
 #include "HierarchicalSigmoidLayer.h"
-
-#include "paddle/math/Bits.h"
+#include "paddle/utils/Util.h"
 
 namespace paddle {
 

paddle/math/Bits.h

-/* Copyright (c) 2016 Baidu, Inc. All Rights Reserve.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License. */
-
-
-#pragma once
-
-#include <type_traits>
-
-namespace paddle {
-
-/**
- * From Facebook folly:
- * https://github.com/facebook/folly/blob/master/folly/Bits.h
- *
- * findLastSet: return the 1-based index of the highest bit set
- *
- * for x > 0:
- * \f[
- *    findLastSet(x) = 1 + \floor*{\log_{2}x}
- * \f]
- */
-template <class T>
-inline constexpr typename std::enable_if<(std::is_integral<T>::value &&
-                                          std::is_unsigned<T>::value &&
-                                          sizeof(T) <= sizeof(unsigned int)),
-                                         unsigned int>::type
-findLastSet(T x) {
-  return x ? 8 * sizeof(unsigned int) - __builtin_clz(x) : 0;
-}
-
-template <class T>
-inline constexpr
-    typename std::enable_if<(std::is_integral<T>::value &&
-                             std::is_unsigned<T>::value &&
-                             sizeof(T) > sizeof(unsigned int) &&
-                             sizeof(T) <= sizeof(unsigned long)),  // NOLINT
-                            unsigned int>::type
-    findLastSet(T x) {
-  return x ? 8 * sizeof(unsigned long) - __builtin_clzl(x) : 0;  // NOLINT
-}
-
-}  // namespace paddle

paddle/math/MatrixBitCode.cpp

@@ -14,7 +14,7 @@ limitations under the License. */
 
 
 #include "paddle/utils/Logging.h"
-#include "Bits.h"
+#include "paddle/utils/Util.h"
 #include "Matrix.h"
 #include "hl_gpu.h"
 

paddle/utils/Util.h

@@ -63,6 +63,18 @@ limitations under the License. */
 
 namespace paddle {
 
+/**
+ * return the 1-based index of the highest bit set
+ *
+ * for x > 0:
+ * \f[
+ *    findLastSet(x) = 1 + \floor*{\log_{2}x}
+ * \f]
+ */
+inline constexpr size_t findLastSet(size_t x) {
+  return x ? 8 * sizeof(unsigned long) - __builtin_clzl(x) : 0;  // NOLINT
+}
+
 /**
  * calculate the non-negative remainder of a/b
  * @param[in] a