1. A method of finding one or more possible matching peptides to a test peptide associated with a tandem mass spectrometry test spectrum s, comprising: selecting a function ƒ that takes spectra s 1 and s 2 as input, where ƒ includes at least one term comprising the number n of peaks that appear in both s1 and a shifted copy of s 2 ; and performing a genetic algorithm on a plurality of candidate peptides using ƒ as the objective function and using s as either s 1 or s 2 .