https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69564
Bug ID: 69564
Summary: lto makes scimark2 LU slower
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: lto
Assignee: unassigned at gcc dot gnu.org
Reporter: vincenzo.innocente at cern dot ch
Target Milestone: ---
mkdir scimark2; cd scimark2
wget http://math.nist.gov/scimark2/scimark2_1c.zip
unzip scimark2_1c.zip
c++ -Ofast *.c; ./a.out
c++ -Ofast *.c -flto; ./a.out
with gcc 4.9.3
gcc version 4.9.3 (GCC)
c++ -Ofast *.c; ./a.out
** **
** SciMark2 Numeric Benchmark, see http://math.nist.gov/scimark **
** for details. (Results can be submitted to p...@nist.gov) **
** **
Using 2.00 seconds min time per kenel.
Composite Score: 2462.90
FFT Mflops: 2070.32 (N=1024)
SOR Mflops: 1661.17 (100 x 100)
MonteCarlo: Mflops: 813.44
Sparse matmult Mflops: 2978.91 (N=1000, nz=5000)
LU Mflops: 4790.64 (M=100, N=100)
[innocent@vinavx3 scimark2]$ c++ -Ofast *.c -flto; ./a.out
** **
** SciMark2 Numeric Benchmark, see http://math.nist.gov/scimark **
** for details. (Results can be submitted to p...@nist.gov) **
** **
Using 2.00 seconds min time per kenel.
Composite Score: 2582.94
FFT Mflops: 2064.19 (N=1024)
SOR Mflops: 1654.04 (100 x 100)
MonteCarlo: Mflops: 1426.90
Sparse matmult Mflops: 2978.91 (N=1000, nz=5000)
LU Mflops: 4790.64 (M=100, N=100)
with latest build
gcc version 6.0.0 20160129 (experimental) (GCC)
[innocent@vinavx3 scimark2]$ c++ -Ofast *.c; ./a.out
** **
** SciMark2 Numeric Benchmark, see http://math.nist.gov/scimark **
** for details. (Results can be submitted to p...@nist.gov) **
** **
Using 2.00 seconds min time per kenel.
Composite Score: 2377.18
FFT Mflops: 1970.89 (N=1024)
SOR Mflops: 1654.04 (100 x 100)
MonteCarlo: Mflops: 810.37
Sparse matmult Mflops: 3328.81 (N=1000, nz=5000)
LU Mflops: 4121.76 (M=100, N=100)
[innocent@vinavx3 scimark2]$ c++ -Ofast *.c -flto; ./a.out
** **
** SciMark2 Numeric Benchmark, see http://math.nist.gov/scimark **
** for details. (Results can be submitted to p...@nist.gov) **
** **
Using 2.00 seconds min time per kenel.
Composite Score: 2136.23
FFT Mflops: 2076.48 (N=1024)
SOR Mflops: 1654.04 (100 x 100)
MonteCarlo: Mflops: 1533.92
Sparse matmult Mflops: 3266.59 (N=1000, nz=5000)
LU Mflops: 2150.13 (M=100, N=100)
