dgesvx segfault

[matheusdiogenesandrade]

Hello again.

I am trying to use the dgesvx function, however, I am having some problems with it. So, I am trying to solve the system Ax = b, for A n by n symmetric. Below I placed an octave code showing the desired operation.

A = [4,1,0.5;1,4,1;0.5,0.5,3.5];
b = [10;15;20];

x = A\b

A * x - b

Which gives the following output.

x_ =
   1.3184
   2.1144
   5.2239

ans =
            0
            0
  -3.5527e-15

So, I tried to replicate the above code in fortran, using the dgesvx function. Below I placed the fortran code.

program dgesvx_example

! SCALAR ARGUMENTS
integer    :: n=3

! ARRAY ARGUMENTS
real(kind=8), dimension(:,:), allocatable :: A, b, x

! LOCAL SCALARS
character(len=1), parameter               :: fact = 'N', trans = 'N', equed = 'N'
integer                                   :: info
real(kind=4)                              :: rcond

! LOCAL ARRAYS
integer, dimension(:), allocatable        :: ipiv, iwork
real(kind=8)                              :: ferr(1), berr(1)
real(kind=8), dimension(:), allocatable   :: r, c, work
real(kind=8), dimension(:,:), allocatable :: af

!
allocate (A(n, n))
allocate (b(n, 1))
allocate (x(n, 1))
allocate (ipiv(n))
allocate (af(n, n))
allocate (r(n))
allocate (c(n))
allocate (work(4 * n))
allocate (iwork(n))

A = reshape((/ 4.0, 1.0, 0.5, 1.0, 4.0, 0.5, 0.5, 1.0, 3.5 /), shape(A))
b = reshape((/ 10.0, 15.0, 20.0 /), shape(b))

do i = 1,n
    do j = 1,n
        write( *, '(e13.6e2)', advance="no") A(i,j)
    end do
    print *, ''
end do

! https://netlib.org/lapack/explore-html-3.6.1/d7/d3b/group__double_g_esolve_ga7091d0af8d314e611bc190d6f515e7ff.html
call dgesvx( &
!     FACT is CHARACTER*1
    fact, &
!     TRANS is CHARACTER*1
    trans, &
!     N is INTEGER
    n, &
!     NRHS is INTEGER
    1, &
!     A is DOUBLE PRECISION array, dimension (LDA,N)
    A, &
!     LDA is INTEGER
    n, &
!     AF is DOUBLE PRECISION array, dimension (LDAF,N)
    af, &
!     LDAF is INTEGER
    n, & 
!     IPIV is INTEGER array, dimension (N)
    ipiv, & 
!     EQUED is CHARACTER*1
    equed, &
!     R is DOUBLE PRECISION array, dimension (N)
    r, &
!     C is DOUBLE PRECISION array, dimension (N)
    c, & 
!     B is DOUBLE PRECISION array, dimension (LDB,NRHS)
    b, &
!     LDB is INTEGER
    n, &
!     X is DOUBLE PRECISION array, dimension (LDX,NRHS)
    x, &
!     LDX is INTEGER
    n, &
!     RCOND is DOUBLE PRECISION
    rcond, &
!     FERR is DOUBLE PRECISION array, dimension (NRHS)
    ferr, &
!     BERR is DOUBLE PRECISION array, dimension (NRHS)
    berr, &
!     WORK is DOUBLE PRECISION array, dimension (4*N)
    work, &
!     IWORK is INTEGER array, dimension (N)
    iwork, & 
!     INFO is INTEGER
    info &
    )

end program dgesvx_example

After compiling the above program gfortran dgesvx_example.f90 -llapack -o main and running it ./main, we obtain the following error.

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

Backtrace for this error:
#0  0x7fb3024259f2 in ???
#1  0x7fb302424b85 in ???
#2  0x7fb30204251f in ???
        at ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
#3  0x7fb3029fee62 in ???
#4  0x55e0475f1013 in ???
#5  0x55e0475f1063 in ???
#6  0x7fb302029d8f in __libc_start_call_main
        at ../sysdeps/nptl/libc_start_call_main.h:58
#7  0x7fb302029e3f in __libc_start_main_impl
        at ../csu/libc-start.c:392
#8  0x55e0475ef144 in ???
#9  0xffffffffffffffff in ???

Interestingly, calling the function dgesv, produces no error.

  call dgesv( &
      n, &
      1, &
      A, &
      n, &
      ipiv, & 
      b, &
      n, &
      info &
      )

Does anyone have any hint for this?

Regards.