From f2feb333843d83b74a9d29f0c73ffe8409795df0 Mon Sep 17 00:00:00 2001
From: Yu Yang <yuyang18@baidu.com>
Date: Thu, 28 Sep 2017 10:50:14 -0700
Subject: [PATCH] Follow comments

---
 paddle/framework/operator.h |  4 ++--
 paddle/platform/place.h     | 11 +++++++++++
 paddle/platform/variant.h   |  2 ++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/paddle/framework/operator.h b/paddle/framework/operator.h
index 4e81d1eaa9d..7d563a3c059 100644
--- a/paddle/framework/operator.h
+++ b/paddle/framework/operator.h
@@ -451,8 +451,8 @@ class OperatorWithKernel : public OperatorBase {
     size_t operator()(const OpKernelKey& key) const {
       int place = key.place_.which();
       int data_type = static_cast<int>(key.data_type_);
-      // NOTE: Number of places limit to 16.
-      int pre_hash = data_type << 4 | (place & 0x0F);
+      int pre_hash = data_type << NUM_PLACE_TYPE_LIMIT_IN_BIT |
+                     (place & ((1 << NUM_PLACE_TYPE_LIMIT_IN_BIT) - 1));
       return hash_(pre_hash);
     }
   };
diff --git a/paddle/platform/place.h b/paddle/platform/place.h
index 1117476bb37..0efc6932349 100644
--- a/paddle/platform/place.h
+++ b/paddle/platform/place.h
@@ -15,6 +15,7 @@ limitations under the License. */
 #pragma once
 
 #include <iostream>
+
 #include "paddle/platform/variant.h"
 
 namespace paddle {
@@ -46,8 +47,18 @@ struct IsGPUPlace : public boost::static_visitor<bool> {
   bool operator()(const GPUPlace &gpu) const { return true; }
 };
 
+// Define the max number of Place in bit length. i.e., the max number of places
+// should be less equal than 2^(NUM_PLACE_TYPE_LIMIT_IN_BIT)
+#define NUM_PLACE_TYPE_LIMIT_IN_BIT 4
+
 typedef boost::variant<GPUPlace, CPUPlace> Place;
 
+// static check number of place types is less equal than
+// 2^(NUM_PLACE_TYPE_LIMIT_IN_BIT)
+BOOST_MPL_ASSERT((boost::mpl::less_equal<
+                  Place::types::size,
+                  boost::mpl::long_<1 << NUM_PLACE_TYPE_LIMIT_IN_BIT>>));
+
 void set_place(const Place &);
 const Place &get_place();
 
diff --git a/paddle/platform/variant.h b/paddle/platform/variant.h
index c2257af1b5d..16ee00efe7a 100644
--- a/paddle/platform/variant.h
+++ b/paddle/platform/variant.h
@@ -29,4 +29,6 @@
 #endif
 #endif
 
+#include <boost/mpl/comparison.hpp>
+#include <boost/mpl/less_equal.hpp>
 #include <boost/variant.hpp>
-- 
GitLab