nop31382 schrieb:
> ----- Original Message -----
> From: Anthony Stone <[log in to unmask]>
> To: Friedrich Hertweck <[log in to unmask]>
> Cc: Van Snyder <[log in to unmask]>;
> <[log in to unmask]>
> Sent: Thursday, June 01, 2000 2:23 PM
> Subject: Re: What do compilers do about assumed-shape dummy arguments?
>
> >
> > At 11:45 on 1 June, Friedrich Hertweck wrote:
> >
> > > Below is a program that does a very simple thing: add the values of
> > > an array and return it. There are four versions of subroutines to
> > > do this:
> > > [etc.]
> >
> > Here are results for Sun's WorkShop 6 beta:
> >
> > f77 loop, contiguous array, sum =32761.333984 time = 12.625000
> > f77 loop, stride 2x2 array, sum =32761.333984 time = 13.437500
> > f90 loop, contiguous array, sum =32761.333984 time = 18.906250
> > f90 loop, stride 2x2 array, sum =32761.333984 time = 19.656250
> > f90 SUM(stride 2x2 array), sum =32761.248047 time = 1.531250
> >
> > A striking time difference in the last case -- but a significant
> > difference in the sum. Repeating the calculation in double precision
> > gives the following:
> >
> > f77 loop, contiguous array, sum =32761.333984 time = 16.750000
> > f77 loop, stride 2x2 array, sum =32761.333984 time = 17.218750
> > f90 loop, contiguous array, sum =32761.333984 time = 23.656250
> > f90 loop, stride 2x2 array, sum =32761.333984 time = 24.218750
> > f90 SUM(stride 2x2 array), sum =32761.248047 time = 3.656250
> >
> > So it isn't a rounding error problem, and the program isn't using
> > different values each time it is run, it would seem.
> >
Was the program compiled with optimization?
If not, this may explain the differences.
Regards,
Friedrich
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