test/test_dmatrix - Increase tolerance and make test more robust

[tamiko]

It turns out that on non-amd64 architectures the test test_dmatrix fails
due to differences in the compared matrices larger than floating point
roundoff errors [1]. Changing the limit from DBL_MIN to 1.0e4 *
DBL_EPSILON [2] (assuming that differences are indeed of the order of
eps) fixes the problem .

[1] https://launchpad.net/~ginggs/+archive/ubuntu/testing/+sourcepub/10330424/+listing-archive-extra
[2] https://en.cppreference.com/w/c/types/limits

[cburstedde]

Thanks! Can you please commit a file doc/author_maier.txt to put your changes to libsc either into the public domain or under the FREEBSD license?

[cburstedde]

Hi, bumping this for the requested author text file. Thanks!

[holke]

Hi.
I can confirm that the dmatrix test fails on an Intel i7-6600U when configured with the C flag

-march=native

Strangely though, it only occurs when running

make -j check

and not with

make check

(any idea why?)

This fix resolves the error.

[cburstedde]

The dependency on -j is weird, but addressed by the fix.

I'll merge it but I cannot do that until I the author_tamiko.txt file is added to put the code under the FreeBSD license.

[cburstedde]

I'll merge it but I cannot do that until I the author_tamiko.txt file is added to put the code under the FreeBSD license.

Hi can I ping you again about this little file? Thanks!

[cburstedde]

Thanks for your proposal! I'm closing this PR though since I don't have the author file.