Segmentation fault when calling a subroutine

[Kate_Johnson]

I am calling the lapack subroutine DLAPMT in the following snippet of my code:

c    Permute matrix c_all according to IPERM1 

    do i=1, n_sources
        do k=1,g_layers
            do l=1,n_layers
            call DLAPMT (.TRUE., nsim, ndim, c_all(:,:,i,k,l), nsim, IPERM1)
            enddo
     
        enddo
    enddo

In this case n_sources is 2, g_layers is 1 and n_layers is 1.  Therefore it should call DLAPMT twice.  The first time it works fine.  The second time it reaches DLAPMT, it kills the process due to a segmentation error. I've checked and all the inputs are exactly the same the second time around.  What could be causing this problem?

Thanks

[Ferdinand_T_]

Hello, for me DLAPMT works fine. Here is an extended (executable) version of your snippet with some randomly choosen values. 

[fortran]

program test
    implicit none
    integer :: i,k,l
    integer :: n_sources, g_layers, n_layers
    integer :: nsim, ndim
    integer, dimension(:), allocatable :: IPERM1
    integer, dimension(:,:,:,:,:), allocatable :: c_all
    
    n_sources = 2
    g_layers = 1
    n_layers = 1

    nsim = 3    ! rows
    ndim = 9    ! columns - permuted

    allocate(c_all(nsim,ndim, n_sources,g_layers,n_layers))
    allocate(IPERM1(ndim))
    IPERM1 = [(i, i=1,ndim)]    ! identical permutation

    do i=1, n_sources
    do k=1,g_layers
    do l=1,n_layers
        call DLAPMT(.TRUE., nsim, ndim, c_all(:,:,i,k,l), nsim, IPERM1)
    enddo     
    enddo
    enddo
end program

[/fortran]

Compiled on ifort 14.0.1 with 'ifort -mkl test.f90' (no segfault)

I can see two possible problems with that call:

• The array c_all is out of bounds for i = 2. This will definitely cause a segfault since lapack relies on the specified dimensions. Did you try to compile with the -check bounds option?
• The permutation is not a valid permutation of [1,2,...,ndim]. You might check that by simply printing IPERM1.

Maybe the Fortran gurus here can come up with a solution if you provide your compiler / lapack version along with a small example program (ready to compile and run) to demonstrate the segfault. (At least, that's what they would ask me for, with similar problems)

Best regards, Ferdinand

[Ferdinand_T_]

Ok, this seems to be a duplicate of http://software.intel.com/en-us/forums/topic/495000 (solved there)

[jimdempseyatthecove]

What are the dimensions of c_all?

IOW is it:  c_all(nsim, ndim, n_sources, g_layers, n_layers)

Jim Dempsey