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Date: Mon, 29 Nov 93 15:02:37 PST
From: ben@age.com (Ben Fahy)
Message-Id: <9311292302.AA23933@toyama.age.com>
To: CRAIGJ@epub.ziff.com
Subject: Re:  Speedup of G4 FAX decoding?
Cc: age!sgi.com!tiff
Sender: tiff-owner@sgi.sgi.com


  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


