There appears to be an threading issue with BLIS compiled with OpenMP and run inside a parallel nested loop.
It crashes the Elk code with a segmentation fault.
I can't reproduce the seg. fault with a small example, but the following program never terminates on our AMD machine:
program test
implicit none
integer, parameter :: n=20
integer i
real(8), allocatable :: a(:,:),b(:,:),c(:,:)
!$OMP PARALLEL DEFAULT(SHARED) &
!$OMP PRIVATE(a,b,c)
!$OMP DO
do i=1,100
allocate(a(n,n),b(n,n),c(n,n))
a=1.d0
b=1.d0
call dgemm('N','N',n,n,n,1.d0,a,n,b,n,0.d0,c,n)
deallocate(a,b,c)
end do
!$OMP END DO
!$OMP END PARALLEL
end program
The above code has to be compiled with
gfortran -fopenmp test.f90 lapack.a libblis.a
Both the number of OpenMP and BLIS threads have to be larger than 1:
export OMP_NUM_THREADS=2
export BLIS_NUM_THREADS=2
If either OMP_NUM_THREADS=1 or BLIS_NUM_THREADS=1 then the code runs fine.
If BLIS is compiled with pthreads:
./configure -t pthreads zen
then the code also runs fine.
The official AMD release (https://developer.amd.com/amd-cpu-libraries/blas-library/) was compiled with OpenMP and therefore also has the bug.
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