Article View: comp.lang.misc
Article #6700Re: optimizations, funny results
From: Preston Briggs
Date: Sat, 10 Feb 1990 19:31
Date: Sat, 10 Feb 1990 19:31
35 lines
1321 bytes
1321 bytes
In article <1990Feb10.160605.25254@ux1.cso.uiuc.edu> mcdonald@aries.scs.uiuc.edu (Doug McDonald) writes:
> subroutine mm(A, B, C, n)
> double precision a(n,n), b(n,n), c(n,n), t
> do 1 i = 1, n
> do 2 j = 1, n
> t = 0.0
> do 3 k = 1, n
> t = t + B(i, k) * C(k, j)
> A(i,j) = t
>3 continue
>2 continue
>1 continue
> end
>Surprised? I sure am. Why should the MIPS Fortran results be so slow?
The Fortran source is incorrect. Correct is:
subroutine mm(A, B, C, n)
double precision a(n,n), b(n,n), c(n,n), t
do 1 i = 1, n
do 2 j = 1, n
t = 0.0
do 3 k = 1, n
t = t + B(i, k) * C(k, j)
3 continue
A(i,j) = t
2 continue
1 continue
end
Note the interchange of the store to A(i,j) and the continue.
Preston
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!cs.utexas.edu!rice!titan!preston From: preston@titan.rice.edu (Preston Briggs) Newsgroups: comp.lang.misc,comp.sys.mips Subject: Re: optimizations, funny results Message-ID: <4895@brazos.Rice.edu> Date: 10 Feb 90 19:31:49 GMT References: <1990Feb10.160605.25254@ux1.cso.uiuc.edu> Sender: root@rice.edu Followup-To: comp.lang.misc Organization: Rice University, Houston Lines: 35