Parameterized shift-and string matching algorithm using super alphabet

In the parameterized string matching, a given pattern P is said to match with a sub-string t of the text T, if there exist a bijection from the symbols of P to the symbols of t. This problem has an important application in software maintenance where it is required to find equivalency between two sections of codes. Two sections of codes are said to be equivalent if one can be transformed into the other by renaming identifiers and variables only. In this paper, we extend shift-and string matching algorithm to find all such occurrences of P in T. The new algorithm is named as parameterized shift-and (PSA) string matching algorithm. We further extend PSA by using the concept of super alphabets. Implementation results show that by using a super alphabet of size s, the algorithm (PSA) is speeded-up by a factor of s, where s is size of the super alphabet (i.e. s is the number of characters processed simultaneously). We also show the performance of super alphabet PSA with respect to duplicity present in the code. However these algorithms are applicable only when pattern length (m) is less than or equal to word length (w) of computer used (i.e. m les w).