GCC 3.4.4

Andrew Haley aph@redhat.com
Fri May 26 16:52:00 GMT 2006


Fritz Jost writes:
 >  
 > I have come across an issue using GCC 3.4.4 which I am in need of
 > help. The problem manifests itself as extremely slow floating point
 > performance for specific arguments passed to the dsin function in
 > FORTRAN using g77. The following statement :
 >  
 >            y = dsin(dble(1.25169754E-06))
 > 
 > when compiled with g77 under GCC 3.4.4 will take 400usec to execute
 > on my 2+ GHz Opteron platform. I have tested several machines and
 > they all show the same problem. The same code executes at sub
 > microsecond speed using GCC 4.0.2 on a Turion-64 notebook as well
 > as a XEON based machine using gcc 3.3.3. Unfortunately changing the
 > GCC version on my project is not an option. Can anybody shed some
 > light on what is going on here ?

Please see http://gcc.gnu.org/ml/gcc-help/2006-05/msg00189.html

That question is about pow() rather than sin(). but the answer is the
same.

See also __dubsin() in glibc/sysdeps/ieee754/dbl-64/dsincos.c.

Andrew.



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