Path: utzoo!attcan!telly!lethe!becker!hybrid!scifi!bywater!uunet!maverick.ksu.ksu.edu!wallace
From: wallace@math.ksu.edu (Wallace Bow)
Newsgroups: comp.benchmarks
Subject: Re: Sun weirdness.
Message-ID: <1990Dec18.012615.2188@maverick.ksu.ksu.edu>
Date: 18 Dec 90 01:26:15 GMT
References: <605@mephisto.edu> <MCCALPIN.90Dec17134832@pereland.cms.udel.edu>
Sender: news@maverick.ksu.ksu.edu (The News Guru)
Distribution: usa
Organization: Sandia National Laboratories, Albuquerque, NM
Lines: 72

In article <MCCALPIN.90Dec17134832@pereland.cms.udel.edu> mccalpin@perelandra.cms.udel.edu (John D. McCalpin) writes:
>> On 17 Dec 90 17:19:00 GMT, juan@burdell.gatech.edu (Juan Orlandini) said:
>>
>> Can anyone tell me why the following program takes only .9 user
>> seconds an .1 sys seconds on a sun 4/370 and 5.0 user seconds
>> and 39.0 sys seconds on sparc 1's (1, 1+, IPC)?
>
>I would guess that it is spending all of its time in a floating-point
>exception handler, since the total time is cut to 2.9 seconds (on a
>Sparc I, no optimization) if you initialize the two arrays before
>using them!

	You guess correctly.  Look at this:

---------------------------------------------------------------------------

Script started on Mon Dec 17 18:16:34 1990
debbie:/home/debbie/wjbow>cat tempfile.c
#include <stdio.h>
#include <floatingpoint.h>

int boom()
{
 printf("Game over!\n");
 exit(-1);
}

main()
{
    int    num_times,row1,col2,col1,num_cols1,num_cols2,num_rows;
    float  mat1[4][4],mat2[4][4],res[4][4];
    float  temp;

    ieee_handler("set","all",boom);

    num_rows = 4;
    num_cols1 = 4;
    num_cols2 = 4;

    for(num_times=0;num_times<10000;num_times++)
    {
      for(row1=0;row1<num_rows;row1++)
      {
        for(col2=0;col2<num_cols2;col2++)
        {
            temp = 0;
            for(col1=0;col1<num_cols1;col1++)
            {
              temp = temp + mat1[row1][col1]*mat2[col1][col2];
            }
            res[row1][col2] = temp;
        }
      }
    }
}
debbie:/home/debbie/wjbow>junk
Game over!
debbie:/home/debbie/wjbow>exit

---------------------------------------------------------------------------

ieee_handler(3M) catches the exception.  See the man page on how to use it
and put it in all of your floating point programs.  It can save you hours
of time with dbx.


--
Wallace J. Bow Jr., wjbow@gorman.cs.sandia.gov

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