diff --git a/(p,t)_sparsification/hash.h b/(p,t)_sparsification/hash.h
new file mode 100644
index 0000000000000000000000000000000000000000..3394fd28f4de154062a068b2340960ea6a60f20c
--- /dev/null
+++ b/(p,t)_sparsification/hash.h
@@ -0,0 +1,43 @@
+//
+// Created by Kiouche on 1/20/2020.
+//
+
+#ifndef P_K_COMPRESSION_HASH_H
+#define P_K_COMPRESSION_HASH_H
+
+
+
+
+#include <string>
+#include <vector>
+
+namespace std {
+
+
+/* Combination hash from Boost */
+    template <class T>
+    inline void hash_combine(size_t& seed, const T& v)
+    {
+        hash<T> hasher;
+        seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+    }
+
+    template<typename S, typename T> struct hash<pair<S, T>>
+{
+    inline size_t operator()(const pair<S, T>& v) const
+    {
+        size_t seed = 0;
+        hash_combine(seed, v.first);
+        hash_combine(seed, v.second);
+        return seed;
+    }
+
+};
+/* End combination hash from Boost */
+
+
+
+}
+
+
+#endif //P_K_COMPRESSION_HASH_H