Re: differences of gfortran on amd64 and i386
<posted & mailed>
Johannes Wiedersich wrote:
> Hello list,
>
> I have a rather funny and annoying problem with a third-party fortran
> program. It is a non-free scientific program for some physical
> calculations. I get different output values, if I compile and run the
> same fortran code on amd64 or i386.
>
> In fact, depending on the input file it exits with some error message in
> i386, when the same file runs fine on amd64. This is even true of the
> 'test' file provided with the program. Therefore it seems there is
> something wrong with my configuration or the compiler on i386.
>
> I can run the binary compiled on i386 on amd64, but the binary compiled
> on amd64 is different and yields different results. The i386-binary runs
> without errors on amd64, however, when it exits on error on i386.
>
> I have no idea, where to start looking for what is wrong here.
>
Is your algorithm stable? One of the characteristics of unstable algorithms
is that they give totally different results when you change precision. try
running the program with single/double precisions and see if there are
significant changes in the results.
also try disabling the optimizations, compile with -Wall, -fbounds-check
options and see if there is any change in the final results.
hth
raju
--
Kamaraju S Kusumanchi
http://malayamaarutham.blogspot.com/
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