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From: chooft@ruunsa.fys.ruu.nl (Rob Hooft)
Newsgroups: comp.sys.sgi
Subject: Benchmarking the SGI: Floating point faster than integer?
Keywords: Benchmark floating integer sgi fortran FLOPS
Message-ID: <1464@ruunsa.fys.ruu.nl>
Date: 11 Sep 90 14:38:27 GMT
Organization: University of Utrecht, Dept. of Physics
Lines: 50

Hello,

As I am planning to buy a PC, I am benchmarking all computers available to
me. On our PI this resulted in a 'pleasant' surprise: Floating point
multiplications are about twice as fast as integer multiplications. Is there
anybody that can explain the results of the following session to me?

Rob Hooft, Chemistry department University of Utrecht, The Netherlands

-----CUT HERE---------------------------------------------------------------
cia:[101]:hooft>cat test.f
      program test
      integer i
      real a,f,g
      integer ia,if,ig
      f=28.0
      g=36.0
      if=28
      ig=36
      t=cputime(0.0)
      do 100 i=1,3000000
100     ia=if*ig
      write(*,*) cputime(t)
      t=cputime(0.0)
      do 200 i=1,3000000
200     a=f*g
      write(*,*) cputime(t)
      t=cputime(0.0)
      do 300 i=1,3000000
300     continue 
      write(*,*) cputime(t)
      end
      function cputime(f)
      real g(2)
      call etime(g)
      cputime=g(1)+g(2)-f
      return
      end
cia:[102]:hooft>f77 -O0 -o test test.f
cia:[103]:hooft>test
    6.340000    
    4.200000    
    2.070000    
12.5u 0.1s 0:15 82%
cia:[104]:hooft>^D
-----CUT HERE---------------------------------------------------------------
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