Program received signal SIGSEGV: Segmentation fault - invalid memory reference. Backtrace for this error:

Question

I have compiled a fortran 95 program in Ubuntu 14.04. Upon running, I got the following error: This is different from:(1)

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

Backtrace for this error:
^Z
[9]+  Stopped                 ./a.out

I even tried

gfortran -g -fcheck=all -Wall DoubExchange.f95

But got the same fault message.

My program:

! HAMILTONIAN Diagonalization for a 2D Lattice of N sites or (N_X) X (N_Y) size, with DOUBLE EXCHANGE.
!                                                       !
            !           D O U B L E    E X C H A N G E                   !
!                                                       !
 PROGRAM DOUBLE_EXCHANGE
   implicit none
   integer:: I, J, K, M, Z, P, L, SIZ, CONT, POINT, S
   integer,parameter :: seed = 8645642
!   character:: N, U
   real*8:: H
   real :: start, finish
!     .. Parameters ..
      INTEGER          N, N_X, N_Y
      INTEGER          LDA
      INTEGER          LWMAX
      PARAMETER        ( LWMAX = 1000 )
!
!     .. Local Scalars ..
!
      INTEGER          INFO, LWORK
!
!     .. Local Arrays ..
!     RWORK dimension should be at least MAX(1,3*N-2)
!
      DOUBLE PRECISION,ALLOCATABLE,DIMENSION(:):: EIG
      REAL*8,ALLOCATABLE,DIMENSION(:,:):: F1
      REAL*8,ALLOCATABLE,DIMENSION(:):: WORK
        call cpu_time(start)
        open(1,file='DOUBLE_EXCHANGE.dat')
        open(2,file='DOUBLE_EXCHANGE.txt')
!
!   We are considering a 2D square lattice of 3 X 3
!
    CALL srand(seed)
    !!  LATTICE DESCRIPTION  !!
    N_X = 2
    N_Y = 2
    SIZ = 2 * N_X * N_Y
    N = SIZ*SIZ
    LDA = N
    !   PROGRAM STARTING POINT  !
    ALLOCATE(F1( SIZ, SIZ ), EIG(SIZ), WORK(3*siz-1))
    CONT = 1
    S = (N_X*2)-1
    M = N_Y-1
DO P=1,1
    DO I=0,M
       DO J=0,S
         POINT = 1
          DO K=0,M
            DO L=0,S
                IF(I==K .AND. ABS(J-L)==2) THEN
                  Z = -1

                ELSE IF(J==L .AND. ABS(I-K)==1) THEN
                  Z = -1

                ELSE IF(J==L .AND. ABS(I-K)==M) THEN
                  Z = -1

                ELSE IF(I==K .AND. ABS(J-L)==S-1) THEN
                  Z = -1

                ELSE IF(I==K .AND. J==L) THEN
                  Z = (-1)**POINT

                ELSE
                  Z = 0                                 !       Potential     0
                ENDIF
            F1(CONT,POINT) = Z
                POINT = POINT + 1
            ENDDO
         ENDDO
            CONT = CONT + 1
       ENDDO
    ENDDO

    WRITE(1,*)
!
       WRITE(1,*),'Displaying Matrix for the given Hamiltonian'
!
       DO i=1,SIZ
            WRITE(1,'(18g15.1)') (F1(i,j), j=1,SIZ)
       ENDDO
!
!
!       DSYEV Example Program Results
!
!   ALLOCATE(WORK(SIZ))
       WRITE(1,*)
       LWORK = -1
       CALL DSYEV( 'Vectors', 'Upper', SIZ, F1, LDA, Eig, WORK, LWORK, INFO )

       LWORK = INT( WORK( 1 ) )

!   DEALLOCATE(WORK)

!   ALLOCATE(WORK(LWORK))
!
!   Solve eigenproblem.
!
       CALL DSYEV( 'Vectors', 'Upper', SIZ, F1, LDA, Eig, WORK, LWORK, INFO )
!
!   Checking for convergence.
!
       IF( INFO.GT.0 ) THEN
          WRITE(*,*)'The algorithm failed to compute eigenvalues.'
          STOP
       END IF
!
!
!       Computes all eigenvalues and, optionally, eigenvectors of an
!       n x n real symmetric matrix A. The eigenvector v(j) of A satisfies
!
!             A*v_i(j) = λ(j)*v_i(j)
!
!
        !!   Print eigenvalues. !!
!
        write(1,*)
        write(1,*)'Eigenvalues'
        write(1,*)
            write(1,'(100g15.5)') (Eig(j), j=1,SIZ)
!
        !!     Print eigenvectors. Where ψ_(i)(eqv. F1(i,j)), i-label is for energy and j-label is for site.   !!
!
        write(1,*)
        write(1,*)'Orthonormal Eigenvectors (stored columnwise)'
        write(1,*)
        do i=1,SIZ
            write(1,'(100g15.5)') (F1(i,j), j=1,SIZ)
        end do
        write(1,*)

!
!        Calculation of number operator, ρ(i) at i-th site for n number of electrons
!
        WRITE(1,*)'Calculation of number operator, ρ(i) at i-th site'
!
!            Considering 3 electrons in the problem
!
    k = INT(SIZ/2)
       CONT = 1
       L    = 1
    DO I=1,SIZ
       H = 0D0
        DO J=1,K
           H = H + F1(I,J)*F1(I,J)     !  WE ARE CALCULATING Σ_n|ψ_n(i)|^2, Where ψ_n(i) are eigenvectors of i-th site with n-component.
        ENDDO
          IF(MOD(I,S) .NE. 0) THEN
             WRITE(2,'(100g15.5)')L,CONT,H
             CONT =CONT + 1

          ELSE
             WRITE(2,'(100g15.5)')L,CONT,H
             WRITE(2,*)
             CONT = 1
             L    = L + 1
          END IF
    ENDDO

        WRITE(1,*)
        WRITE(1,*)
        WRITE(1,*)
ENDDO
! 900    format (F8.3,F8.3)
          call cpu_time(finish)
              print '("Time = ",f6.3," seconds.")',finish-start
              write(1, '("Time = ",f6.3," seconds.")'),finish-start
       STOP
END PROGRAM

So, error is mostly about, correct initialization of WORK.

Did you try `-fbacktrace` or running your program through a debugger? — Alexander Vogt, Sep 27 '14 at 16:23
How through debugger, I don't know about that. Not -fbacktrace — L.K., Sep 27 '14 at 16:24
I got this, I don't know about it. Program received signal SIGSEGV, Segmentation fault. 0x00007ffff6fdebaf in _int_free (av=0x7ffff731e760 , p= , have_lock=0) at malloc.c:3996 3996 malloc.c: No such file or directory. (gdb) Quit — L.K., Sep 27 '14 at 16:33
Did you mean this: gfortran -fbacktrace -g DoubExch.f95 -lblas -llapack — L.K., Sep 27 '14 at 16:36
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/62041/discussion-between-lavkush-and-alexander-vogt). — L.K., Sep 27 '14 at 16:43
I don't know much, can you help me in this issue. Its an important program, baffling me. I tried a lot, wasted lot of time, but got nowhere. Please consider this. — L.K., Sep 27 '14 at 16:53
Did you try both `-g` and `-fbacktrace` and also `-fcheck=all -Wall `? What means "it didn't work"? I have debugged many programs succesfully with these options and with valgrind. — Vladimir F Героям слава, Sep 28 '14 at 07:47

score 3 · Answer 1 · answered Sep 29 '14 at 10:24

Yes, the error is about WORK. You are requesting and using the optimal value of LWORK from your DSYEV workspace query but you aren't resizing WORK accordingly. (You have the resizing code there but it is commented out.)

I ran through the NAG Fortran Compiler with -C=all -C=undefined enabled:

Runtime Error: dsyev.f90, line 1: Invalid reference to procedure DSYEV - Dummy array WORK (number 7) has 80 elements but actual argument only has 23 elements

(I had to link against an LAPACK that had also been built with -C=undefined.)

score 0 · Accepted Answer · answered Sep 30 '14 at 06:22

Thank You for the knowledge of WORK.

But I sort out the error, in my program. Problem was because of initialization of LDA = N(where, N = siz*siz), as result my matrix F1(siz,siz*siz),more than allocation.

So, I just need to initialize LDA = siz.

Problem was resolved.

Program received signal SIGSEGV: Segmentation fault - invalid memory reference. Backtrace for this error:

2 Answers2