diff --git a/CMakeLists.txt b/CMakeLists.txt
index e35d643e..1a6aaa9d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -118,8 +118,8 @@ if (UNIX)
 else()
     install(FILES ${CMAKE_BINARY_DIR}/$<$<CONFIG:Release>:Release>$<$<CONFIG:Debug>:Debug>/ion-core.dll DESTINATION bin)
     install(FILES ${CMAKE_BINARY_DIR}/$<$<CONFIG:Release>:Release>$<$<CONFIG:Debug>:Debug>/ion-core.lib DESTINATION lib)
-    
-    # These lines is for backward compatibility. 
+
+    # These lines is for backward compatibility.
     # TODO: Deprecate old name of dll/lib.
     install(FILES ${CMAKE_BINARY_DIR}/$<$<CONFIG:Release>:Release>$<$<CONFIG:Debug>:Debug>/ion-core.dll DESTINATION bin RENAME ion.dll)
     install(FILES ${CMAKE_BINARY_DIR}/$<$<CONFIG:Release>:Release>$<$<CONFIG:Debug>:Debug>/ion-core.lib DESTINATION lib RENAME ion.lib)
@@ -152,7 +152,7 @@ endif()
 # Packaging
 #
 if (UNIX)
-    set(CPACK_GENERATOR "DEB")
+    set(CPACK_GENERATOR "TGZ" "DEB")
     set(CPACK_DEBIAN_FILE_NAME DEB-DEFAULT)
     set(CPACK_DEBIAN_PACKAGE_MAINTAINER "Fixstars Corporation Inc.")
     configure_file(${CMAKE_SOURCE_DIR}/ion-kit.pc.in ${CMAKE_BINARY_DIR}/ion-kit.pc @ONLY)
@@ -167,4 +167,4 @@ message(STATUS "Version: ${GIT_DESCRIBE_RESULT}")
 string(STRIP "${GIT_DESCRIBE_RESULT}" ION_KIT_VERSION_S)
 string(REPLACE "v" "" ION_KIT_VERSION ${ION_KIT_VERSION_S})
 set(CPACK_PACKAGE_VERSION ${ION_KIT_VERSION})
-include(CPack)
\ No newline at end of file
+include(CPack)
diff --git a/include/ion/port_map.h b/include/ion/port_map.h
index 2ce02f8a..c6c4c3e8 100644
--- a/include/ion/port_map.h
+++ b/include/ion/port_map.h
@@ -1,12 +1,37 @@
 #ifndef ION_PORT_MAP_H
 #define ION_PORT_MAP_H
 
+#include <functional>
 #include <string>
+#include <tuple>
 
 #include <Halide.h>
 
 #include "ion/util.h"
 
+namespace std
+{
+
+template<>
+struct hash<tuple<string, string>>
+{
+    std::size_t operator()(const tuple<string, string>& k) const noexcept
+    {
+        return std::hash<std::string>{}(std::get<0>(k)) ^ std::hash<std::string>{}(std::get<1>(k));
+    }
+};
+
+template<>
+struct equal_to<tuple<string, string>>
+{
+    bool operator()(const tuple<string, string>& v0, const tuple<string, string>& v1) const
+    {
+        return (std::get<0>(v0) == std::get<0>(v1) && std::get<1>(v0) == std::get<1>(v1));
+    }
+};
+
+} // std
+
 namespace ion {
 
 /**
@@ -14,24 +39,6 @@ namespace ion {
  */
 class PortMap {
 
-    using key_t = std::tuple<std::string, std::string>;
-
-    struct key_hash : public std::unary_function<key_t, std::size_t>
-    {
-        std::size_t operator()(const key_t& k) const
-        {
-            return std::hash<std::string>{}(std::get<0>(k)) ^ std::hash<std::string>{}(std::get<1>(k));
-        }
-    };
-
-    struct key_equal : public std::binary_function<key_t, key_t, bool>
-    {
-        bool operator()(const key_t& v0, const key_t& v1) const
-        {
-            return (std::get<0>(v0) == std::get<0>(v1) && std::get<1>(v0) == std::get<1>(v1));
-        }
-    };
-
 public:
 
     template<typename T>
@@ -142,7 +149,7 @@ class PortMap {
         return param_func_.at(k);
     }
 
-    std::unordered_map<key_t, std::vector<Halide::Buffer<>>, key_hash, key_equal> get_output_buffer() const {
+    std::unordered_map<std::tuple<std::string, std::string>, std::vector<Halide::Buffer<>>> get_output_buffer() const {
         return output_buffer_;
     }
 
@@ -154,7 +161,7 @@ class PortMap {
 
     std::unordered_map<std::string, Halide::Expr> param_expr_;
     std::unordered_map<std::string, Halide::Func> param_func_;
-    std::unordered_map<key_t, std::vector<Halide::Buffer<>>, key_hash, key_equal> output_buffer_;
+    std::unordered_map<std::tuple<std::string, std::string>, std::vector<Halide::Buffer<>>> output_buffer_;
     Halide::ParamMap param_map_;
 };