|Re: [eigen] 3.1.4 & 3.0.7 on Friday?|
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On Thu, 1 Aug 2013, Rhys Ulerich wrote:
./build/test/product_trmm_21' causes a repeatable failure for all
I cannot reproduce. Does it fails for this seed only?
It failed on several seeds for me. Using 'while
./build/test/product_trmm_21 ; do echo WORKED ; done' will let your
CPU crank on it until either you find one that breaks or you get bored
I can reproduce it, with the same seed, both for the new 3.1.4 and the
current dev branch.
I haven't looked at it in detail yet, but the test compares two ways of
computing A - B, where A is a given matrix and B is a product involving a
triangular matrix. For some reason, there is a lot of cancellation going
on, even though these are big random matrices. The norm of A and B are
both about 300, but the norm of A - B is 0.019 and norm of the difference
of computing A - B with both methods is 6e-5 (here, norm is the Kronecker
norm, the sqrt of sum of squares). The test compares 6e-5 with 0.019 and
fails, but arguably it should compare it with 300 and succeed.
So my guess is that the failure is nothing serious, but it's a tad
preliminary at the moment, and I need to stop now.