There is an issue with the routine zheevd when compiled with Intel fortran using the optimization-O2 or-O3.

The problem occurs at line 285 of dlaed4:

DELTA( J ) = ( D( J )-D( I ) ) - TAU

which evaluates to zero because of the compiler not respecting the parenthesis. This results in a division-by-zero later on. Including-assume protect_parens fixes the problem.

Here is a simple program which produces the error:

program testimplicit noneinteger, parameter :: n=27integer i,jinteger liwork,lrwork,lwork,infointeger, allocatable :: iwork(:)real(8), allocatable :: w(:),rwork(:)complex(8), allocatable :: a(:,:),work(:)liwork=5*n+3lrwork=2*n**2+5*n+1lwork=n**2+2*nallocate(w(n),a(n,n))allocate(iwork(liwork),rwork(lrwork),work(lwork))a(:,:)=0.d0do i=1,n  a(i,i)=1.d0  do j=i+1,n    a(i,j)=cos(dble(i))  end doend docall zheevd('V','U',n,a,n,w,work,lwork,rwork,lrwork,iwork,liwork,info)print *,'info',infoend program

I'm not sure whether this is a compiler, LAPACK or user issue. I've added-assume protect_parens to our code (elk.sourceforge.net) and made zheev as the default eigenvalue solver for the moment.