Optimal Parallel Two Dimensional Text Searching on a CREW PRAM

We present a parallel algorithm for two dimensional text searching over a general alphabet. This algorithm is optimal in two ways. First, the total number of operations on the text is linear. Second, the algorithm takes time O(log m) on a CREW PRAM (where m is the length of the longest dimension of the pattern), thus matching the lower bound for string matching on a PRAM without concurrent writes. On a CRCW, the algorithm runs in time O(log log m). ] 1998 Academic Press