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October 1994

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1994.10.11 20:05 "g4 decomp. improved (3.3beta ALPHA 021)", by Kyriakos Georgiou

According to my experiments G4 decompression is about 16.4% faster 
going from 3.3beta ALPHA 015 to 3.3beta ALPHA 021 on a particular test
target I am using, but hopefully on most images.  Earlier I reported 
~3% gains, but it was just after time'ing the reading of just one 
g4 tiff under the old and new libtiff's (dont shoot me, I know that
was bad 8).  This time I run a tight loop of 32 images. 

I have 32 IEEE Std 167A-1987 Faxcsimilie test chart tiff images which
are already scanned.  I made two versions of all of them, compressed 
and uncompressed.  I compiled TIFF 3.3beta ALPHA 015 and 
TIFF 3.3beta ALPHA 021 under a 90Mhz P5 running Linux with 32Mb ram 32Mb
swap.  I used the pentium gcc with -mpentium -O4. (Makefile.gcc)

Then I recompiled a program that is optimised to the best of my
programing ability :^) that reads the test chart tiffs, and evaluates
scanning quality (what it does is not important, I just wanted to see
the speedup in I/O).  Anyway, there is no speedup when the images are
compressed (logical), but g4 compression reading is a bit faster, this
program runs about 16.4% faster on the same data, with 3.3beta ALPHA 021.

Timings for reading all 32 images:

TIFF 3.3beta ALPHA 015
----------------------
uncompressed:
0.71user 1.65system 0:02.36elapsed 100%CPU
compressed:
22.03user 0.85system 0:23.09elapsed 99%CPU


TIFF 3.3beta ALPHA 021
----------------------
uncompressed:
0.71user 1.63system 0:02.38elapsed 98%CPU
compressed:
18.67user 1.00system 0:19.84elapsed 99%CPU


regards,
--Kyriakos