module m_randrot
contains
subroutine randrot(V,nrens)
   implicit none
   integer, intent(in)  :: nrens
   real,    intent(out) :: V(nrens,nrens)

   real, dimension(nrens,nrens) :: U, A, B
   real sigma(nrens), work(10*nrens)
   real, parameter :: pi=3.14159253589
   integer ierr, iens

   call random_number(B)
   call random_number(A)
   B = sqrt(-2.*log(A)) * cos(2.*pi*B)

!$OMP CRITICAL
   call dgesvd('N', 'A', nrens, nrens, B, nrens, sigma, U, nrens, V, nrens, work, 10*nrens, ierr)
!$OMP END CRITICAL
   if (ierr /= 0) print *, 'randrot: ierr',ierr

end subroutine randrot
end module m_randrot