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The FFTW version 2 libraries on HECToR are only available for the
Portland Group compiler, so the full FFT comparison tests were
performed exclusively with pgf90. Cray's LibSci (10.2.1) was used for BLAS and
LAPACK. The following compiler flags were used throughout the FFT tests:
-fastsse -O3 -Mipa
In order to measure the performance of the FFT routines specifically
we used Castep's internal Trace module to profile the two subroutines
wave_recip_to_real_slice and
wave_real_to_recip_slice. These subroutines take a group
of eigenstates, called a wavefunction slice, and Fourier transform
them from reciprocal space to real space, or vice versa.
Figure 3.1:
Graph showing the relative performance of the four FFT
subroutines available to Castep on HECToR for the TiN benchmark. This
benchmark transforms wavefunction slices to real space 1634 times and
back again.
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As can be seen from figure 3.1 FFTW 3.1.1 was the
fastest FFT library available on HECToR.
Sarfraz A Nadeem
2008-09-01