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Re: GCC options and floating-point correctness (benchmarks)
- From: Scott Robert Ladd <coyote at coyotegulch dot com>
- To: Theodore Papadopoulo <Theodore dot Papadopoulo at sophia dot inria dot fr>
- Cc: gcc mailing list <gcc at gcc dot gnu dot org>
- Date: Thu, 25 Mar 2004 13:36:14 -0500
- Subject: Re: GCC options and floating-point correctness (benchmarks)
- References: <200403251805.i2PI5ung011979@mururoa.inria.fr>
Theodore Papadopoulo wrote:
coyote@coyotegulch.com said:
I produced the following results for a C version of PARANOIA on a
2.8GHz Pentium 4 (Northwood core), HT enabled, using a very recent
build of the tree-ssa branch. I'll be glad to send copies of the
benchmark source to anyone who requests it privately.
Do you have those for intel's compiler ??
icc -o paranoiai -xN -tpp7 paranoia.c
icc -o paranoiai -xN -tpp7 -mp1 paranoia.c
icc -o paranoiai -xN -tpp7 -mp paranoia.c
icc -o paranoiai -xN -tpp7 -ipo paranoia.c
icc -o paranoiai -xN -tpp7 -mp1 paranoia.c
icc -o paranoiai -xN -tpp7 -mp paranoia.c
icc -o paranoiai -xN -tpp7 -O1 paranoia.c
icc -o paranoiai -xN -tpp7 -O2 paranoia.c
icc -o paranoiai -xN -tpp7 -O3 paranoia.c
icc -o paranoiai -xN -tpp7 -O1 -ipo paranoia.c
icc -o paranoiai -xN -tpp7 -O2 -ipo paranoia.c
icc -o paranoiai -xN -tpp7 -O3 -ipo paranoia.c
icc -o paranoiai -xN -tpp7 -O1 -ipo -mp1 paranoia.c
icc -o paranoiai -xN -tpp7 -O2 -ipo -mp1 paranoia.c
icc -o paranoiai -xN -tpp7 -O3 -ipo -mp1 paranoia.c
icc -o paranoiai -xN -tpp7 -O1 -ipo -mp paranoia.c
icc -o paranoiai -xN -tpp7 -O2 -ipo -mp paranoia.c
icc -o paranoiai -xN -tpp7 -O3 -ipo -mp paranoia.c
(no failures)
(no serious defects)
(no defects)
The number of FLAWs discovered = 1.
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Yes, I checked to see if the code changed with each combination of
options; it did. In fact, the "flaw" is different with different options.
With -mp, the single test that failed was:
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Sticky bit used incorrectly or not at all.
FLAW: lack(s) of guard digits or failure(s) to correctly round or chop
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Without -mp, the single flaw was:
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FLAW: X = 3.05947655544740190e-308
is not equal to Z = 2.22507385850720138e-308 .
yet X - Z yields 0.00000000000000000e+00 .
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Given that GCC exhibits FAILURES and DEFECTS, even under the best of
circumstances, suggests that ICC may have a leg up when it comes to this
benchmark.
--
Scott Robert Ladd
Coyote Gulch Productions (http://www.coyotegulch.com)
Software Invention for High-Performance Computing