How to measure distance between two data

OK .... actually this table is some samples taken from user A represent in trigraphs from any text he wrote and digit behind it be the time he take to type those trigraphs such as ( acs--125 ms, asd--200 ms ........) build a sorted table1(S1) ,(sorted according to the time), consists of these data and table2 (S2) of the same trigraphs

compare between these samples and found the distance between the same trigraphs from the two samples i should make it in vhdl code , but you make me in doubt what i use ram or registers.

regarding you code about register how i can find index in vhdl code.