On 4 Jun 2012, at 23:56, Thomas Weber wrote: > Eh no, not quite. We usually look at the errors and decide. But here we > are talking about a factor of 10000 between expected and actual result. > That's a bug.
As far as I understand from Lukas' explanation, the sign in the result is not relevant. The failures I get are of the form: ***** assert (Mo, Me, 1e-4); !!!!! test failed assert (Mo,Me,1e-4) expected -0.23910 0.30720 1.16300 1.19670 -1.04970 -2.97090 -0.23910 2.62700 3.10270 -3.70520 0.00000 0.00000 -0.51370 -1.28420 0.82230 0.00000 0.00000 0.15190 -0.51370 0.74350 -0.44660 0.01430 -0.47800 -0.20130 0.02190 but got -0.23915 0.30723 1.16297 -1.19671 1.04965 -2.97091 -0.23915 2.62702 -3.10273 3.70515 0.00000 0.00000 -0.51368 1.28421 -0.82227 0.00000 0.00000 -0.15189 -0.51368 0.74348 0.44660 -0.01427 0.47803 -0.20129 0.02190 maximum absolute error 7.41035 exceeds tolerance 0.0001 If I take the abs () of the results I have >> abs (Mo) - abs (Me) ans = -5.0000e-05 -3.0000e-05 3.0000e-05 -1.0000e-05 5.0000e-05 -1.0000e-05 -5.0000e-05 -2.0000e-05 -3.0000e-05 5.0000e-05 0.0000e+00 0.0000e+00 2.0000e-05 -1.0000e-05 3.0000e-05 0.0000e+00 0.0000e+00 1.0000e-05 2.0000e-05 2.0000e-05 0.0000e+00 3.0000e-05 -3.0000e-05 1.0000e-05 0.0000e+00 so results are well within the expected tolerance. Of course if the abs is left out of the test the error looks much larger as x - (- x) = 2 * x so I'd really prefer the assert above to be changed to "assert (abs (Mo), abs (Me), 1e-4);" to avoid confusing error messages. > I also don't buy the argument that ATLAS and BLAS will produce wildly > differing results that are both correct. Whenever the differences > between ATLAS and BLAS were huge in the past, there was a bug in the > library or in the calling code. As to why the sign of the result is not predictable, I do not know enough about the algorithm being implemented here to comment. Lukas, could you point to the specific BLAS routine that is giving different results here? c. ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Octave-dev mailing list Octave-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/octave-dev
