CRC options

[restokes86]

Please forgive me if this is obvious, but what is the difference between "Consider files with same CRC identical" and "Consider files with different CRCs different"? They seem like the exact inverse of each other. Help is completely opaque on the topic, and I found nothing illuminating on the forum.

Randy

[psguru]

The "Consider files with ... identical" and "Consider files with ... different" sets of options speed up comparison by letting ExamDiff Pro take "shortcuts" rather than comparing each pair of files. The way that the options work is that every time ExamDiff Pro reaches a pair of matching files, it goes through the list of enabled options and tries to come to a conclusion - if the results are still inconclusive, then ExamDiff Pro must perform full comparison on the pair of files.

With this in mind, let's examine the effects of the "Consider files with same CRC identical" and "Consider files with different CRCs different" options (assuming that all other options under Options | Dir Comparison | Type Of File Comparison are disabled):

- If both options are disabled, then of course ExamDiff Pro doesn't bother even calculating the files' CRCs (unless the user sets CRCs to be displayed under Options | Dir Columns)
- If only the former is enabled, then, for each pair of files, ExamDiff Pro calculates and compares the CRCs. If they are identical, then ExamDiff Pro simply marks them as identical. If they are different, then ExamDiff Pro performs full comparison on them.
- In only the latter is enabled, then, for each pair of files, ExamDiff Pro calculates and compares the CRCs. If they are different, then ExamDiff Pro simply marks them as different. If they are identical, then ExamDiff Pro performs full comparison on them.
- If both options are enabled, then, for each pair of files, ExamDiff Pro calculates and compares the CRCs, and the files are marked identical or different solely from the CRC comparison.

As you can see, the options, while very similar, do have slight nuances. In almost all situations, it would make sense to either have them both enabled or both disabled.

[MSpagni]

Maybe an example like this can be enligthening:
If you have two files with the same CRC it's very probable (in practice: certain) that the files are identical.
If the two files have different CRC, even if they're not identical perhaps they can still be considered equal (e.g. "ignore blank lines" or "ignore white spaces").

[restokes86]

Thank you both -- that was very helpful. Perhaps a note in the documentation? (hint hint)

Randy