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From: "burnus at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/31139] sum(w_re(1:nn,1)*fi(i(1:nn, ii))) up to 3.5x slower than C version
Date: Mon, 12 Mar 2007 08:16:00 -0000 [thread overview]
Message-ID: <20070312081639.23202.qmail@sourceware.org> (raw)
In-Reply-To: <bug-31139-13404@http.gcc.gnu.org/bugzilla/>
------- 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
next prev parent reply other threads:[~2007-03-12 8:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-11 22:38 [Bug fortran/31139] New: " burnus at gcc dot gnu dot org
2007-03-11 22:45 ` [Bug fortran/31139] " burnus at gcc dot gnu dot org
2007-03-11 22:50 ` burnus at gcc dot gnu dot org
2007-03-12 5:33 ` pinskia at gcc dot gnu dot org
2007-03-12 5:38 ` pinskia at gcc dot gnu dot org
2007-03-12 7:58 ` burnus at gcc dot gnu dot org
2007-03-12 8:16 ` burnus at gcc dot gnu dot org [this message]
2007-04-18 5:56 ` fxcoudert at gcc dot gnu dot org
2010-09-12 15:45 ` jvdelisle at gcc dot gnu dot org
[not found] <bug-31139-4@http.gcc.gnu.org/bugzilla/>
2013-06-22 16:55 ` dominiq at lps dot ens.fr
2015-10-10 9:21 ` dominiq at lps dot ens.fr
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