Build problem on Red Hat Enterprise 6

[susilehtola]

Hi,

I'm trying to update the Fedora and Red Hat OpenBLAS packages to 0.2.20, but for some reason it fails to build on the Red Hat Enterprise Linux 6 branch. The problem I'm seeing is a bunch of errors [1] like

/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../lib64/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: ld returned 1 exit status
make[1]: *** [dblat3] Error 1

This happens even though I have the NO_AVX2=1 flag set.

[1] https://kojipkgs.fedoraproject.org//work/tasks/4289/21074289/build.log

[martin-frbg]

Can you build an earlier version in the same environment ? Without NO_AVX2 you would get assembler errors, this here looks like maybe you have mismatched versions of gcc and gfortran installed.

[brada4]

Can you share spec and patches, they seem for different openblas version.

[susilehtola]

It actually looks like the build started on EL6 failing right after I added the patch that adds necessary flags to make the tests compile correctly on another distribution, where the tests of the OpenMP flavor library weren't linking properly with the OpenMP runtime libraries.

The up-to-date spec and patches are all available at
https://src.fedoraproject.org/rpms/openblas/tree/el6

I'll see if it compiles when I don't apply patch3.

[susilehtola]

... and the packages in the buildroot can be seen at
https://kojipkgs.fedoraproject.org//work/tasks/4289/21074289/root.log

so gcc (and gfortran) is 4.4.7-18.el6.

[susilehtola]

Removing patch3 didn't help, I still get

/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../lib64/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: ld returned 1 exit status
make[1]: *** [sblat1] Error 1

[martin-frbg]

Obviously "main" is in the respective source files sblat2.f etc that it just compiled, I can only imagine there might be an ABI mismatch of some kind (even if it just a matter of underscores appended to module names). Hence the question about compiler versions. I'd try a plain and simple build from the source tarball without your .spec file and rpmbuild environment first to see if the build platform is sane.

[brada4]

crt1.o is part of static glibc or so.
Upd: looks like something else static is missing.
Upd: planting SCL devtools as leads to same place.
Upd (last) OpenMP only problem, other configs build just fine

[brada4]

Oops - @susilehtola your build log links faded away.....
Two questions:

• Do tests run before you plant old static lapack or after?
• I think there is a bug not affecting you that gfortran imports pthread lib which at best does not serve any purpose whatsoever in OMP build

[susilehtola]

The GNU OpenMP implementation is based on pthreads, so I'm not sure the latter is a problem.

As to your first question, I don't really understand what you're asking: the package doesn't use "old static lapack", but uses the LAPACK sources that are shipped with OpenBLAS.

[brada4]

Yes, but blank OMP build succeeds, but not rpmbuild.
It should be indifferent if it is -lpthread added there or not.
I will spend some time understanding the difference that breaks stuff.

[susilehtola]

The crt1.o error just says that for some reason, sblat1 ends up without a main() function; that is, there's no PROGRAM in Fortran lingo.

[brada4]

I am flipping (your) parameters one by one to see which one turns golden. I can easily produce failed rpmbuild with log.

[brada4]

@susilehtola it turns out static gfortran -fopenmp as used to link tests in your SPEC requires additional -lpthread on centos6
I need to test 3 other combinations, but this is bare minimum to make it through.

Not related to this request... Do you think it s possible for you to implement AVX2 support https://github.com/xianyi/OpenBLAS/wiki/faq#binutils based on that RHEL6 once met Haswell?
It is like double _gemm speed or so...

[susilehtola]

@brada4 thanks, I'll check if it builds with -lpthread.

As for the second one, it's not possible to compile Fedora EPEL packages with packages not in the RHEL repository. For AVX2 support, one just has to upgrade to RHEL7.

[brada4]

You can add -lpthread universally, it does no damage as long as it stays linux, there are even some pthread calls mixed into omp code paths.