A method, a computer system, and/or a computer program product are disclosed. One computer-implemented method for building a hash table includes dividing a hash table into plural blocks; and dividing each block into plural sub-blocks. A certain sub-block uses a first pattern, of association between a key and a location for storing the key. Another sub-block which belongs to the same block having the certain sub-block uses a second pattern which is different from the first pattern. The method may further include building a bash table by using memory blocks in a Field Programmable Gate Array.