A student working in DNA research had the task of finding repeated sequences of M values in a long sequence of values:

ACTCGGATCTTGCATTTCGGCAATTGGACCCTGACTTGGCCA ...

Wrote the simplest (and therefore, most efficient?) program:

DO 10 I = 1, N-M DO 10 J = I+1, N-M FOUND = .TRUE. DO 20 K = 1, M 20 IF X[I+K-1] .NE. X[J+K-1] THEN FOUND = .FALSE. IF FOUND THEN ... 10 CONTINUE

Took a depressingly long time.

This story is continued on the next slide.