use of pointer or allocatable array

lxh37 · ‎09-10-2014

I developed an web applet in Ruby On Rails in MAc OSX, and have the computation part written in Fortran.
I wrapped Fortran by C and be able to call it from Ruby. I tested FORTRAN codes with a simple
console application and I can call it from Ruby as long as I don't call it using a thread.
When I called it using a thread, it crashes in function "prob" at line
if( ran_genmn(rand, tmp1, tmp2, tmp3, err ) == RETURN_FAIL )

I commented out all codes inside function ran_genmn, it still crashes.

codes:

real(our_dble) function prob( n, delta, conf, rand, err ) result( answer )
   use program_constants
   use random_generator
   implicit none

   .....

   real(our_dble), target :: one1( niter, 4 ), big_R( niter, 4), Sigma( 4, 4 )
   real(our_dble), pointer :: tmp1(:,:), tmp2(:,:), tmp3(:,:)

   ...
   nullify( tmp1, tmp2, tmp3 )
   ...
   do i=1,100

   ....
   tmp1 => big_R ! set pointers before passing them to genmn
   tmp2 => one1
   tmp3 => Sigma
   if( ran_genmn(rand, tmp1, tmp2, tmp3, err ) == RETURN_FAIL ) then
   answer = -1.d0
   return
   end if
   nullify( tmp1, tmp2, tmp3 ) ! clear the pointers
   ....
   end do
   ...
   return
   end function prob

   integer(our_int) function ran_genmn(gendata, x, mean, cov, &
   err ) result(answer)
   ...
   real(kind=our_dble), pointer :: mean(:,:), cov(:,:)
   real(kind=our_dble), pointer :: x(:,:), chol(:,:)
   ...

   ! local variables
   character(len=*), parameter :: subname = "ran_genmn"
   integer(kind=our_int) :: i, j, k, n, p, status
   real(kind=our_dble), allocatable :: rtmp(:)

....
end function ran_genmn

After I changed one1 to allocatable array:
real(kind=our_dble), allocatable :: one1(:,:)
and change function ran_genmn as:

   integer(our_int) function ran_genmn(gendata, n, p, x, mean, cov, &
   err ) result(answer)
   ....
   integer(our_int), intent(in) :: n, p
   real(kind=our_dble), intent(in) :: mean(n,p)
   real(kind=our_dble), pointer :: cov(:,:)
   real(kind=our_dble), pointer :: x(:,:), chol(:,:)
   ....
   end function ran_genmn

Then I have no problem to call it using a thread, I wonder why I can't use pointer for variable
one1 similar as the other two variables x and cov, the difference for one1 and the other two variables in function ran_genmn
is that one1 is only needed as input, the other two are computed inside ran_genmn.