g77 bug?

Toon Moene toon@moene.indiv.nluug.nl
Fri Nov 1 14:27:00 GMT 2002

Jean-Pierre.Eckmann@physics.unige.ch wrote:

> This seems to be an optimization bug in g77/gcc
> With Optimization <= O1 (only on file escape.f) the program gives
> different results  from optimizing O2

This sounds like the known problem that, on ix86 processors, sometimes 
increasing optimisation levels will result in more variables being kept 
in (80-bit) floating point registers, which will yield different 
rounding after operations and different results.

On my powerpc-unknown-linux-gnu system, compilations with g77 -O0 
escape.f and g77 -O2 escape.f give identical results.

Kind regards,

Toon Moene - mailto:toon@moene.indiv.nluug.nl - phoneto: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
Maintainer, GNU Fortran 77: http://gcc.gnu.org/onlinedocs/g77_news.html
Join GNU Fortran 95: http://g95.sourceforge.net/ (under construction)

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