pb with -ffast-math
Alain Baeckeroot
alain.baeckeroot at laposte.net
Tue Apr 14 02:54:48 CDT 2009
Hi
i builded octave with additional optimisation flags
> FFLAGS = -O -mieee-fp -march=native
> XTRA_CFLAGS = -mieee-fp -march=native
> XTRA_CXXFLAGS = -mieee-fp -march=native
Adding just -march=native is fine, and it seems that the build
is significantly faster (10-20%) than the one shipped with my distro
(debian lenny 32bit, on core2duo T5550)
All tests are OK (but 2 expected failures).
when i add the -ffast-math option, it builds, but segfault at runtime:
$ make
...
Octave successfully built. Now choose from the following:
./run-octave - to run in place to test before installing
make check - to run the tests
make install - to install
make[1]: quittant le répertoire « /opt/octave-3.0.5 »
$ ./run-octave
** On entry to octave parameter number 13 had an illegal value
Erreur de segmentation
1/ Is it normal ?
2/ Are there some optimisation flags i should set to
improve speed. We have numerous independant short computations, and
need no precision (2 significant digit is good enought)
I thought to add -funsafe-math-optimizations -ffinite-math-only ,
but only after trying simpler stuff.
And this is really not important, i doubt we can get another 20%
speed improvement.
Alain.
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