On Tue, Jul 24, 2012, steinbrt.rci.rutgers.edu wrote:
> Intel Compilers but not with gcc. I could track it down to a point in
> subroutine sc_pscale in softcore.F90 where we have
>
> x(1,i) = x(1,i) + xmolnu - xmol
>
> This is rigid translation of atom coordinates for pressure scaling, xmolnu
> and xmol are the old and new box dimensions. The two numbers are quite
> similar, so the subtraction involves loss of precision of about five
> digits. That is not a problem per se, but this loss of precision results
> in arbitrary lowest digits when the subtraction is done in intel-compiled
> code.
>
> e.g.
>
> xmolnu 40.3614616595491
> -xmol -40.3635833689616
> should be
> = -0.0021217094125
> but is
> = -0.002121709412506334 on process V0
> and
> = -0.002121709412520545 on process V1
>
First: are you sure that x(1,i), xmolnu, and xmol are exactly the same on V0
and V1?
Second: try adding -fltconsistency and/or -fp-model precise to the flags for
the Intel compile. Does that make any difference?
...dac
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Received on Tue Jul 24 2012 - 15:00:05 PDT
