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