Author: njn
Date: 2008-02-11 21:22:15 +0000 (Mon, 11 Feb 2008)
New Revision: 7401
Log:
notes about SPEC benchmarks
Added:
trunk/docs/internals/SPEC-notes.txt
Added: trunk/docs/internals/SPEC-notes.txt
===================================================================
--- trunk/docs/internals/SPEC-notes.txt (rev 0)
+++ trunk/docs/internals/SPEC-notes.txt 2008-02-11 21:22:15 UTC (rev 7401)
@@ -0,0 +1,43 @@
+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.
+
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