4. The computer system of claim 2 , wherein the processor is further configured to: form feature masks using the first gap vectors, wherein each of the feature masks represents a different one of the signature groups.
4. The computer system of claim 2 , wherein the processor is further configured to: form feature masks using the first gap vectors, wherein each of the feature masks represents a different one of the signature groups. 5. The computer system of claim 4 , wherein the processor is further configured to: compare the second gap vector of the input string with one or more feature masks of the signature groups.