diff --git a/Database/Join.cpp b/Database/Join.cpp
index aa0e675..d2c2d0d 100644
--- a/Database/Join.cpp
+++ b/Database/Join.cpp
@@ -132,7 +132,9 @@ Join::judge(int _smallest, int _biggest)
 	//BETTER:how to guess the size of can_lists
 	double size = (_smallest + _biggest) / 2.0;
 	double ans = Join::PARAM_DENSE * dense - size / Join::PARAM_SIZE;
-	if (ans > Join::JUDGE_LIMIT)
+	double limit = 1.0 / (double)Join::JUDGE_LIMIT;
+	//if (ans > Join::JUDGE_LIMIT)
+	if (ans > limit)
 		return 0;	//multi_join method
 	else
 		return 1;	//index_join method
diff --git a/Database/Join.h b/Database/Join.h
index 41d8eca..07dbb43 100644
--- a/Database/Join.h
+++ b/Database/Join.h
@@ -55,8 +55,12 @@ private:
 	static const unsigned PARAM_SIZE = 1000000;
 	static const unsigned PARAM_PRE = 10000;
 	static const unsigned PARAM_DENSE = 1;
-	static const double JUDGE_LIMIT = 0.5;
+
+	//constexpr needed in C++11 (or in newer g++)
+	//static const double JUDGE_LIMIT = 0.5;
+	static const int JUDGE_LIMIT = 2;  //use 1.0/JUDGE_LIMIT
 	static const int LIMIT_CANDIDATE_LIST_SIZE = 1000;
+
 	//BETTER?:predefine size to avoid copy cost
 	TableType current_table;
 	TableIterator new_start;   //keep to end() as default
diff --git a/api/cpp/example/Makefile b/api/cpp/example/Makefile
index 71a97ea..246bd49 100644
--- a/api/cpp/example/Makefile
+++ b/api/cpp/example/Makefile
@@ -1,5 +1,5 @@
-#CC=g++
-CC=ccache g++
+CC=g++
+#CC=ccache g++
 
 example: CppAPIExample.o
 	$(CC) -o example CppAPIExample.o -L../lib -lgstoreconnector
diff --git a/api/cpp/src/Makefile b/api/cpp/src/Makefile
index 273be35..37abdf3 100644
--- a/api/cpp/src/Makefile
+++ b/api/cpp/src/Makefile
@@ -1,5 +1,5 @@
-#CC=g++
-CC=ccache g++
+CC=g++
+#CC=ccache g++
 
 lib_dir=../lib/
 socket_obj_dir=../../../.objs/
diff --git a/makefile b/makefile
index 2d27bda..7e51351 100644
--- a/makefile
+++ b/makefile
@@ -35,8 +35,9 @@
 
 #compile parameters
 
-CC = ccache g++
-#CC = g++
+# WARN: maybe difficult to install ccache in some systems
+#CC = ccache g++
+CC = g++
 
 #the optimazition level of gcc/g++
 #http://blog.csdn.net/hit_090420216/article/details/44900215