The location of a bug resulting from processing a sequence of input files is determined by generating a potentially smaller sequence of the files which result in the bug. Such files can include data, instruction, or both. The smaller sequence can be determined by excluding portions from the sequence, and or returning portions to the sequence, and testing the sequence to determine if it results in the bug. In one embodiment of the present invention, excluded and returned portions become successively smaller by about a quotient of two. In another embodiment, individual files are excluded from a sequence of files, preferably in reverse order to their appearance in the sequence of files. The resulting sequence is tested to determine if it results in the bug. If not, the file can be returned to the sequence, and the bug location method continued with another file of the sequence.