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why do I keep getting this response from my Fortran code?

+9 votes
asked May 22, 2024 by Amatullah Ali (250 points)
Error termination. Backtrace:
#0  0x7f2c54b2aad0 in ???
#1  0x7f2c54b2b649 in ???
#2  0x7f2c54b2c27f in ???
#3  0x7f2c54d7b1f6 in ???
#4  0x7f2c54d7b4ed in ???
#5  0x55f2418a7fef in ???
#6  0x55f2418a875e in ???
#7  0x7f2c54908d8f in __libc_start_call_main
        at ../sysdeps/nptl/libc_start_call_main.h:58
#8  0x7f2c54908e3f in __libc_start_main_impl
        at ../csu/libc-start.c:392
#9  0x55f2418a7114 in ???
#10  0xffffffffffffffff in ???

1 Answer

+1 vote
answered May 23, 2024 by Peter Minarik (101,360 points)
selected May 27, 2024 by Amatullah Ali
 
Best answer

Seems like an invalid memory address (0xffffffffffffffff).

Can you please share your code?

commented May 23, 2024 by Amatullah Ali (250 points)
PROGRAM ABCD
    IMPLICIT NONE
    INTEGER ::  N
    PARAMETER (N = 51)
    INTEGER ::  NM1, NM2, NP1, NP2, INTR, N1
    REAL :: DY, DT, CC, TT, AA, PR, SC, TIMEI, STABR, TIMMAX, TIM
    REAL, DIMENSION(N) :: U, T, C, Y, A1, B1, C1, D1, XX
    INTEGER :: I, J, NINT

    OPEN (UNIT=6, FILE='rmigri2024.out', STATUS='NEW')

    ! Initialization of constants
    SC = 0.5
    PR = 0.71
    TT = 8.0
    CC = 2.0
    AA = 100.0
    TIMEI = 0.5
    STABR = 1.0
    TIMMAX = 4.0

    WRITE (6,10)
10  FORMAT (' N  CC  TT  ')
    WRITE (6,20) N, CC, TT, PR
20  FORMAT (I4, 3F8.2)

    NM1 = N - 1
    DY = 1.0 / REAL(NM1)
    DT = STABR * DY * DY
    INTR = INT(TIMEI / DT)
    NINT = 0
    N1 = 0
    TIM = 0.0

    Y(1) = 0.0
    DO I = 1, NM1
        Y(I+1) = Y(I) + DY
    END DO

    DO I = 1, N
        T(I) = 0.0
        U(I) = 0.0
        C(I) = 0.0
    END DO

    C(1) = 0.5
    C(N) = -0.5
    U(N) = 0.0
    U(1) = 1.0

    DO I = 1, NM1/10
        N1 = N1 + 1
        NINT = NINT + 1
        TIM = TIM + DT

        CALL FLTEMP(NM1, DY, DT, PR, T, A1, B1, C1, D1, XX)
        CALL FLCON(NM1, DY, DT, SC, CC, TT, AA, T, C, A1, B1, C1, D1, XX)
        CALL FLVEL(NM1, DY, DT, -0.8, U, T, C, A1, B1, C1, D1, XX)

        IF (NINT == INTR) THEN
            WRITE (6,30) TIM
30          FORMAT ('Time = ', F8.2)
            DO J = 1, N, NM1/10
                WRITE (6,40) Y(J), U(J), T(J), C(J)
40              FORMAT (F6.2, 3E20.7)
            END DO
            CALL HTC(NM1, DY, U, C)
            NINT = 0
        END IF

        IF (TIM >= TIMMAX) EXIT
    END DO

    CLOSE (UNIT=6)

    STOP
END PROGRAM ABCD

SUBROUTINE FLTEMP(NM1, DY, DT, PR, T, A1, B1, C1, D1, XX)
    IMPLICIT NONE
    INTEGER :: NM1
    REAL :: DY, DT, PR, DTYP
    REAL, DIMENSION(*) :: T, A1, B1, C1, D1, XX
    INTEGER :: I, J

    DTYP = DT / (PR * DY * DY)

    DO I = 2, NM1
        A1(I-1) = DTYP
        B1(I-1) = -1.0 - 2.0 * DTYP
        C1(I-1) = DTYP
        D1(I-1) = -T(I)
    END DO

    D1(1) = D1(1) - A1(1) * T(1)
    D1(NM1) = D1(NM1) - C1(NM1) * T(NM1+1)

    CALL THOMAS(NM1, A1, B1, C1, D1, XX)

    DO J = 2, NM1
        T(J) = XX(J-1)
    END DO

    RETURN
END SUBROUTINE FLTEMP

SUBROUTINE FLCON(NM1, DY, DT, SC, CC, TT, AA, T, C, A1, B1, C1, D1, XX)
    IMPLICIT NONE
    INTEGER :: NM1
    REAL :: DY, DT, SC, CC, TT, AA, DTYP, CC1
    REAL, DIMENSION(*) :: T, C, A1, B1, C1, D1, XX
    INTEGER :: I, J

    DTYP = DT / (SC * DY * DY)
    CC1 = 1.0 / (DY * DY)

    DO I = 2, NM1
        A1(I-1) = DTYP
        B1(I-1) = -1.0 - 2.0 * DTYP
        C1(I-1) = DTYP
        D1(I-1) = -C(I) - AA * DT * (CC1 * ((C(I) + CC) / (T(I) + TT) * (T(I+1) - 2.0 * T(I) + T(I-1)) &
                  + 1.0 / 4.0 * ((C(I+1) - C(I-1)) * (T(I+1) - T(I-1)) / (T(I) + TT)) &
                  - ((C(I) + CC) * (T(I+1) - T(I-1))**2 / (4.0 * (T(I) + TT)**2))))
    END DO

    D1(1) = D1(1) - A1(1) * C(1)
    D1(NM1) = D1(NM1) - C1(NM1) * C(NM1+1)

    CALL THOMAS(NM1, A1, B1, C1, D1, XX)

    DO J = 2, NM1
        C(J) = XX(J-1)
    END DO

    RETURN
END SUBROUTINE FLCON

SUBROUTINE FLVEL(NM1, DY, DT, AB, U, T, C, A1, B1, C1, D1, XX)
    IMPLICIT NONE
    INTEGER :: NM1
    REAL :: DY, DT, AB, DTYP
    REAL, DIMENSION(*) :: U, T, C, A1, B1, C1, D1, XX
    INTEGER :: I, J, N

    DTYP = DT / DY**2

    DO I = 2, NM1
        A1(I-1) = DTYP
        B1(I-1) = -1.0 - 2.0 * DTYP
        C1(I-1) = DTYP
        D1(I-1) = -U(I) - DT * (T(I) + (AB * C(I)))
    END DO

    D1(1) = D1(1) - A1(1) * U(1)
    D1(NM1) = D1(NM1) - C1(NM1) * U(N)

    CALL THOMAS(NM1, A1, B1, C1, D1, XX)

    DO J = 2, NM1
        U(J) = XX(J-1)
    END DO

    RETURN
END SUBROUTINE FLVEL

SUBROUTINE HTC(NM1, DY, U, C)
    IMPLICIT NONE
    INTEGER :: NM1
    REAL :: DY, DY2, SKIN0, SKIN1, SHK0, SHK1
    REAL, DIMENSION(*) :: U, C

    DY2 = 2.0 * DY
    SKIN0 = (U(2) - U(1)) / DY
    SKIN1 = (U(NM1+1) - U(NM1)) / DY
    SHK0 = (C(2) - C(1)) / DY
    SHK1 = (C(NM1+1) - C(NM1)) / DY

    WRITE (6,50) SKIN0, SHK0
50  FORMAT ('Stanton number at y = 0 is', F10.5, ' ', F10.5)
    WRITE (6,60) SKIN1, SHK1
60  FORMAT ('Stanton number at y = 1 is', F10.5, ' ', F10.5)

    RETURN
END SUBROUTINE HTC

SUBROUTINE THOMAS(NM1, A, B, C, D, X)
    IMPLICIT NONE
    INTEGER :: NM1, I
    REAL, DIMENSION(*) :: A, B, C, D, X
    REAL, DIMENSION(NM1) :: CP, DP

    CP(1) = C(1) / B(1)
    DP(1) = D(1) / B(1)

    DO I = 2, NM1
        CP(I) = C(I) / (B(I) - A(I) * CP(I-1))
        DP(I) = (D(I) - A(I) * DP(I-1)) / (B(I) - A(I) * CP(I-1))
    END DO

    X(NM1) = DP(NM1)
    DO I = NM1-1, 1, -1
        X(I) = DP(I) - CP(I) * X(I+1)
    END DO

    RETURN
END SUBROUTINE THOMAS
commented May 24, 2024 by Peter Minarik (101,360 points)
I never worked with Fortran, so all I know is from other programming experiences.

I played a bit with your code and similar error would occur if I try to run your code with the output file already existing. The error is because you specified that the file should not exist ('NEW')

OPEN (UNIT=6, FILE='rmigri2024.out', STATUS='NEW')

But even deleting the output file the error happens.

More debugging revealed the next error could happen in FLVEL on line

D1(NM1) = D1(NM1) - C1(NM1) * U(N)

Again, I'm not a Fortran programmer, so I'm not familiar with assumed-size arrays. But at least this gives you a location where to look for the issue.

I found the problem by commenting out code to see what works and what not until I found the line that allows execution if commented out but produces an error if left uncommented.

If you've found the problem and the fix, please share it so others can learn something here.

Good luck!
commented May 27, 2024 by Amatullah Ali (250 points)
•    I changed the STATUS='NEW' to STATUS='REPLACE' in the OPEN statement to ensure that the file is overwritten if it already exists.
•    I added a new subroutine CHECK_IEEE_FLAG() to encapsulate the check for floating-point exceptions, making it easier to maintain and call from multiple places.
commented May 27, 2024 by Peter Minarik (101,360 points)
Thanks for sharing your solution. I'm glad you're sorted now!
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