[gambit-list] New gcc and gambit

Bradley Lucier lucier at math.purdue.edu
Fri Apr 1 18:27:53 EDT 2011


I've just built the latest fftw3 with gcc-4.6.0 (it uses the compiler
options -O3 -fast-math) and compared it to gambit-4.6.0 (without any
updates) configured with

./configure CC='/pkgs/gcc-4.6.0/bin/gcc -fschedule-insns'

For both systems we computed an fft of $2^{25}$ complex elements.  The
scheme code did an "out-of-place" fft, fftw3 does an "in-place" fft, but
I can't see any way to get fftw3 to do an "out-of-place" fft, even
though there are reports of such a code on the BenchFFT web site.

The results are

Gambit:

    2730 ms cpu time (2730 user, 0 system)

FFTW3:

With FFTW_ESTIMATE (estimate the best algorithm without any actual
testing):

4.5400000000000000e+00 seconds

With FFTW_PATIENT (compute the specific size FFT we want to do with many
different algorithms, then choose the fastest one):

2.9500000000000002e+00 seconds

Brad

PS:  The total time for the code that tests many different algorithms is

1587.630u 4.840s 26:34.24 99.8%	0+0k 0+0io 0pf+0w





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