[Numpy-discussion] numpy and roundoff(?)

Lisandro Dalcin dalcinl@gmail....
Tue Mar 4 09:26:50 CST 2008

Damian Eads wrote:
> One used -mfpmath=sse, and the other, -mfpmath=387.
> Keeping them both
> the same cleared the discrepancy.

Oh yes! I think you  got it...

On 3/3/08, Christopher Barker <Chris.Barker@noaa.gov> wrote:
> Was it really a "significant" difference, or just noticeable? I hope
>  not, that would be pretty scary!

I now believe that this is possible causing the trouble. And yes, in
my case the cummulative differences leaded to different iteration
counts in a matrix-free Newton-Krylov method. Of course, the final
answer was as as accurate as the tolerances for the nonlinear solver.

Lisandro Dalcín
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
PTLC - Güemes 3450, (3000) Santa Fe, Argentina
Tel/Fax: +54-(0)342-451.1594

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