Mail Archives: djgpp/1997/02/10/14:39:58
From: | frabb AT worldaccess DOT nl
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Newsgroups: | comp.os.msdos.djgpp
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Subject: | Antw: timing instructions [code, LONG]
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Date: | Mon, 10 Feb 97 12:47:41 GMT
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Organization: | World Access, Internet, E-mail and Videotex
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Lines: | 47
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Message-ID: | <N.021097.134741.15@skn2-11.worldaccess.nl>
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References: | <5dlh98$qrl AT gummy DOT cs DOT indiana DOT edu>
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NNTP-Posting-Host: | skn2-11.worldaccess.nl
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To: | djgpp AT delorie DOT com
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DJ-Gateway: | from newsgroup comp.os.msdos.djgpp
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Aan 9-02-97 22:58, in bericht <5dlh98$qrl AT gummy DOT cs DOT indiana DOT edu>, Jeff Standish
<jestandi AT cs DOT indiana DOT edu> schreef:
> Now, my question is, if you look at the two sets of results below, you'll
> see than they are almost identical, _except_ for integer +/-, which
> literally takes twice as long to run when Win95 is installed. I'm
> baffled by the result.
When running your program several imes under win 3.11 I got inconsistent
results. I think win does other things in the middle of your timingloop, I even
got negative values several times!
> MS-DOS Win95 (instructions per second)
> -------- --------
> int +: 33217359 16326061
> int -: 33221636 16386937
>
I think the results of sinf are invalid:
> sinf(): 1444230 1429516
> for (index = 0; index < ITERATIONS; ++index) {
> f1 = sin(f2); f1 = sin(f2); f1 = sin(f2); f1 = sin(f2);
> f1 = sin(f2); f1 = sin(f2); f1 = sin(f2); f1 = sin(f2);
> }
> t2 = uclock();
> for (index = 0; index < ITERATIONS; ++index) {
> f1 = sinf(f2); f1 = sinf(f2); f1 = sinf(f2); f1 = sinf(f2);
> f1 = sinf(f2); f1 = sinf(f2); f1 = sinf(f2); f1 = sinf(f2);
> f1 = sinf(f2); f1 = sinf(f2); f1 = sinf(f2); f1 = sinf(f2);
> f1 = sinf(f2); f1 = sinf(f2); f1 = sinf(f2); f1 = sinf(f2);
> }
you are subtracting 8*sin from 8*sinf!
> -----------------------------------------------------------------------------
> Jeff Standish http://www.cs.indiana.edu/hyplan/jestandi.html
>
I added my favourite, long double, to your program. I am rather confused by the
results. Is there any Intel publication available of the inner workings of the
Pentium fpp?
frank abbing
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