From: Nicholas Nethercote <njn@valgrind.org>
Date: Mon, 11 Feb 2008 21:22:15 +0000 (+0000)
Subject: notes about SPEC benchmarks
X-Git-Tag: svn/VALGRIND_3_4_0~1068
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=f3b38367f039bdf599fee2237b65d73728975a7a;p=thirdparty%2Fvalgrind.git

notes about SPEC benchmarks


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@7401
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diff --git a/docs/internals/SPEC-notes.txt b/docs/internals/SPEC-notes.txt
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+From Vince Weaver:
+
+I've been running the SPEC CPU 2006 benchmarks under valgrind (doing some
+work on my BBV generating plugin).
+
+There are two benchmarks that have issues, and I thought I'd share them
+here for future reference.
+
+1). zeusmp - does not run
+
+    It has a 1GB data segment, which valgrind cannot handle on a 32-bit
+    CPU.
+
+2). dealII - runs forever, never ending
+
+    It took a while, but I tracked this down to a 64bit/80bit
+    floating point issue.
+
+    The code in the QGauss<1>::QGauss() function has some code like this:
+
+    const long double tolerance = std::max (static_cast<long double>
+       (std::numeric_limits<double>::epsilon() / 100),
+       static_cast<long double>(std::numeric_limits<long
+       double>::epsilon() *5));
+
+     do {
+       ....
+       various fp operations
+       ....
+     } while (abs(p1/pp) > tolerance);
+
+
+     The tolerance in this case is being set to ~2.22e-18, but the
+     abs(p1/pp) value never gets below ~2.586e-17 under valgrind.
+
+     [This is because Valgrind only uses 64-bit FP values on x86, not 80-bit
+     values.]
+
+     This is similar to an issue that happens with the "art"
+     benchmark on SPEC CPU 2000, but in the "art" case it only
+     makes the code take longer to finish; this "dealII" problem
+     makes the benchmark loop forever.
+