finally, managed to get the results, but the problem is, though hashes are fast, ordering the sequence in a problem with hash. i had mentioned in my query in one of the example sets i have given which is >2 geneid2. the >2_2 must come in the second position only. even by using tie::hash, i can not do this. coz, the tie hash will follow the order of input file. what do i do in this case ?? plz suggest.