Simplifying compiler optimization flags logic (fortran compilers)
Hi,
I was wondering whether it was really worth having a lot of magic going on in fcompilers for flags like -msse2 and co (everything done in get_flags_arch, for example). It is quite fragile (we had several problems wrt buggy compilers, buggy CPU detection), and I am not sure it buys us much anyway. Did some people notice a difference between gfortran -O3 -msse2 and gfortran -O3 ?
thanks,
David
On Fri, Oct 31, 2008 at 05:25, David Cournapeau david@ar.media.kyoto-u.ac.jp wrote:
Hi,
I was wondering whether it was really worth having a lot of magic going on in fcompilers for flags like -msse2 and co (everything done in get_flags_arch, for example). It is quite fragile (we had several problems wrt buggy compilers, buggy CPU detection), and I am not sure it buys us much anyway. Did some people notice a difference between gfortran -O3 -msse2 and gfortran -O3 ?
You're probably right.
On Sat, Nov 1, 2008 at 1:07 AM, Robert Kern robert.kern@gmail.com wrote:
On Fri, Oct 31, 2008 at 05:25, David Cournapeau david@ar.media.kyoto-u.ac.jp wrote:
I was wondering whether it was really worth having a lot of magic going on in fcompilers for flags like -msse2 and co (everything done in get_flags_arch, for example). It is quite fragile (we had several problems wrt buggy compilers, buggy CPU detection), and I am not sure it buys us much anyway. Did some people notice a difference between gfortran -O3 -msse2 and gfortran -O3 ?
You're probably right.
I think it is probably best to take out some of the magic in fcompilers as well.
Jarrod Millman wrote:
On Sat, Nov 1, 2008 at 1:07 AM, Robert Kern robert.kern@gmail.com wrote:
Hi,
On Fri, Oct 31, 2008 at 05:25, David Cournapeau david@ar.media.kyoto-u.ac.jp wrote:
I was wondering whether it was really worth having a lot of magic going on in fcompilers for flags like -msse2 and co (everything done in get_flags_arch, for example). It is quite fragile (we had several problems wrt buggy compilers, buggy CPU detection), and I am not sure it buys us much anyway. Did some people notice a difference between gfortran -O3 -msse2 and gfortran -O3 ?
You're probably right.
we removed setting the various SSE flags in Sage's numpy install because they caused segfaults when using gfortran. I don't think that there is a significant performance difference with SSE for that code because we use Lapack and ATLAS build with SSE when it is available.
I think it is probably best to take out some of the magic in fcompilers as well.
Cheers,
Michael
Michael Abshoff wrote:
Jarrod Millman wrote:
On Sat, Nov 1, 2008 at 1:07 AM, Robert Kern robert.kern@gmail.com wrote:
Hi,
On Fri, Oct 31, 2008 at 05:25, David Cournapeau david@ar.media.kyoto-u.ac.jp wrote:
I was wondering whether it was really worth having a lot of magic going on in fcompilers for flags like -msse2 and co (everything done in get_flags_arch, for example). It is quite fragile (we had several problems wrt buggy compilers, buggy CPU detection), and I am not sure it buys us much anyway. Did some people notice a difference between gfortran -O3 -msse2 and gfortran -O3 ?
You're probably right.
we removed setting the various SSE flags in Sage's numpy install because they caused segfaults when using gfortran. I don't think that there is a significant performance difference with SSE for that code because we use Lapack and ATLAS build with SSE when it is available.
I think it is probably best to take out some of the magic in fcompilers as well.
Cheers,
Michael _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Hi, I just wanted to point out that the man page on Linux and the GCC manual for i386 and x86 options (http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/i386-and-x86_002d64-Options.html...) states: "For the i386 compiler, you need to use -march=cpu-type, -msse or -msse2 switches to enable SSE extensions and make this option effective. For the x86-64 compiler, these extensions are enabled by default." "This is the default choice for the x86-64 compiler."
While this is still a relatively few proportion of processors and I do not know when GCC started this, the sse flags should be redundant and thus removed as more people use x86_64 processors.
Bruce
participants (5)
-
Bruce Southey -
David Cournapeau -
Jarrod Millman -
Michael Abshoff -
Robert Kern