Quite true. In my case the resync points (after ignoring or stripping header lines) can be as little as a blank line followed by a single matching record in the areas of the file where the differences occur, so maybe SuperC isn't seeing enough lines of resync to work correctly.
OTOH the GNUWIN32 diff utility on my laptop found all of the differences without a problem, so it can be done, just not apparently by SuperC. Peter -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Joel C. Ewing Sent: Tuesday, January 08, 2013 2:23 PM To: [email protected] Subject: Re: SuperC utility loses its place when comparing text files with many differences <Snipped> This is a inherent problem with any algorithm which attempts to flag/detect changes between files and do it with minimum resource consumption. Your typical algorithm compares two files and when a difference is detected starts looking through subsequent records in both files for a "resync" point where both files match up again, with trivial false resync points typically eliminated by requiring a resync point to have "n" consecutive records match. There problem is that for any "n", one can create cases where "false" matches would be found, or if the changes are too massive, no resync point may be found. We humans would like the algorithm to find the "best" resync point, which would probably be defined as one which minimizes the total changes reported for the two files, but it is unclear how one could compute this without a recursive algorithm that exhaustively tries all possible resync points and doesn't just accept the first one found. Humans looking at two files that have frequently recurring patterns interspersed with unique records can intuitively tune out the repetitive patterns and look at the unique records when looking for a best resync points, but building those smarts into a formal algorithm may not be feasible. -- Joel C. Ewing, Bentonville, AR [email protected] -- This message and any attachments are intended only for the use of the addressee and may contain information that is privileged and confidential. If the reader of the message is not the intended recipient or an authorized representative of the intended recipient, you are hereby notified that any dissemination of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by e-mail and delete the message and any attachments from your system. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
