------- Comment #6 from burnus at gcc dot gnu dot org 2007-03-12 08:16 -------
> Can someone try instead of doing "__real__ a += w[j] *__real__ mfi[*index];"
> Use "a+= xxx* yyy" and also use -std=c99 to get the correct multiplication?
Well, -std=c99 was used already and the "real(!) * complex" calculation was
already correct. "c_cmplx" below uses now:
a += w[j ] * mfi[*index++];
Compiled with:
gcc -std=c99 -O3 -funroll-loops -ftree-vectorize -march=opteron -msse3
-ffast-math -m64
gfortran -O3 -funroll-loops -ftree-vectorize -march=opteron -msse3 -ffast-math
-m64
Fortran: 0.4360271
Fortran: 0.4280267
c_nosse: 0.2440166
c_nosse: 0.2320151
c_sse: 0.2320137
c_sse: 0.2400150
c_struct: 0.2320151
c_struct: 0.2320147
c_cmplx: 0.2360163
c_cmplx: 0.2320147
And using a non-manually unrolled version: 0.3760242, 0.3760242
for(i = 0; i < np ; i++) {
for(j = 1; j < n; j++)
a += w[j ] * mfi[*index++];
fo[i] = a;
}
Thus the unrolling seems to do most of the speed up. With -funroll-all-loops,
the timings of fortran an the non-unrolled version remain the same.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31139
