1 From Vince Weaver: 2 3 I've been running the SPEC CPU 2006 benchmarks under valgrind (doing some 4 work on my BBV generating plugin). 5 6 There are two benchmarks that have issues, and I thought I'd share them 7 here for future reference. 8 9 1). zeusmp - does not run 10 11 It has a 1GB data segment, which valgrind cannot handle on a 32-bit 12 CPU. 13 14 2). dealII - runs forever, never ending 15 16 It took a while, but I tracked this down to a 64bit/80bit 17 floating point issue. 18 19 The code in the QGauss<1>::QGauss() function has some code like this: 20 21 const long double tolerance = std::max (static_cast<long double> 22 (std::numeric_limits<double>::epsilon() / 100), 23 static_cast<long double>(std::numeric_limits<long 24 double>::epsilon() *5)); 25 26 do { 27 .... 28 various fp operations 29 .... 30 } while (abs(p1/pp) > tolerance); 31 32 33 The tolerance in this case is being set to ~2.22e-18, but the 34 abs(p1/pp) value never gets below ~2.586e-17 under valgrind. 35 36 [This is because Valgrind only uses 64-bit FP values on x86, not 80-bit 37 values.] 38 39 This is similar to an issue that happens with the "art" 40 benchmark on SPEC CPU 2000, but in the "art" case it only 41 makes the code take longer to finish; this "dealII" problem 42 makes the benchmark loop forever. 43 44
