1993.11.29 22:02 "Speedup of G4 FAX decoding?", by Craig Jackson

1993.11.29 23:02 "Re: Speedup of G4 FAX decoding?", by Ben Fahy

My profiling of G4 FAX decoding with 3.3beta2 seems to point a finger at subroutine call overhead as a significant factor using VAX C on VMS. In particular, the finddiff routine in tif_fax3.c, which is a wrapper for the findspan routine in the same file, shows up a lot in the profiling.

Has anybody considered replacing finddiff with an equivalent macro?

Tried it and found any benefit?

In the X windows Image Extension sample implementation, we removed all unnecessary subroutine calls from our FAX code and got significant performance improvements (greater than 10%). I assume you would get similar gains with the TIFF code. I don't know if finddiff is the only one that should be removed.

Ben Fahy
AGE Logic, Inc