Share allocatable Arrays - arrays

Question

I have some allocatable arrays which I need to share between some subroutines. I usually would just pass them as arguments or maybe write everything in a Module, but I'm afraid this isn't possible in my situation.
I only write some own subroutines and use subroutines provided and described by an FEM-Solver. So i cannot alter the arguments of this subroutines or wrap them in a Module.
As far as i know it also isn't possible to Build common blocks with array of unknown size at compile time.
Is there something else to pass my arrays?
Update:
At the moment my program environment looks like this:
I have a subroutine, provided by the FEM-program, which is called after each increment, this calls several of my subroutines where I compute some values for each node or for a subset of those.
To display these values in the post-Simulation, i have to pass them to another subroutine. This subroutine is called by the FEM-solver for each node at the end of the increment. So shifting my code to this Subroutine would produce a lot of overhead.
My idea is to compute the values once, store the Values in an array and pass this array to the second subroutine where they will be written to the database of the computation.
Update
Some Pseudo-code:
Assumed from program behaviour:
Program FEM-solver
*magic*
call ENDINC(ar1,ar2)
*something*
do NodeID=1,Sum_Of_Nodes
do valueID=1,Sum_Of_User_Computed_Values !(defined in preprocessing)
call nodeval(NodeID,valueID,Value,ar3,...,arN)
end do
end do
*voodoo*
end program FEM-solver
Written and working:
Subroutine ENDINC(ar1,ar2)
*Computation of some node values*
*Calling of own Subroutines, which compute more values*
*Writing an array with results values for some/each node(s)*
nodersltArr(NodeID,rslt)=*some Value*
end Subroutine ENDINC
Needed, writng the computed Values to the Node solution database:
Subroutine nodeval(NodeID,valueID,Value,ar3,...,arN)
*called for each NodeID and valueID*
value=noderslArr(NodeID,valueID)
end subroutine nodeval

Answer 1

You can pass an allocatable array to procedure that isn't declared to use allocatable arrays, as long as the array is allocated before the call. (Of course, you can't use the array as an allocatable array in the procedure in which it is declared without that property.) Perhaps that will solve your problem. Allocate the array in the code that you write, than pass it as an argument to the FEM solver.
Example code: (I'd normally put the function into a module but you say that you can't do that, so I write an example showing the case of not using a module.)
function MySum ( RegArray )
real :: MySum
real, dimension (:), intent (in) :: RegArray
MySum = sum (RegArray)
end function MySum
program TestArray
implicit none
interface AFunc
function MySum ( SomeArray )
real :: MySum
real, dimension (:), intent (in) :: SomeArray
end function MySum
end interface AFunc
real, dimension (:), allocatable :: AllocArray
integer :: N
real :: answer
write (*, '("Input array size: ")', advance="no")
read (*, *) N
allocate ( AllocArray (1:N) )
AllocArray = 1.0
answer = MySum ( AllocArray )
write (*, *) answer
end program TestArray
---------- EDIT: Second Concept ---------
Sharing an allocatable array between two subroutines, without the calling routine being "aware" of the array.
module MySubs
real, allocatable, dimension (:,:) :: array
contains
subroutine One ( x, y, ... N, M )
integer, intent (in) :: N, M
if ( .NOT. allocated (array) ) allocate ( array (N, M) )
end subroutine One
subroutine Two ( .... )
end subroutine Two
end module MySubs
UPDATE: note: This approach can be used to pass information between the two routines without the main program having access the module ... for the question, without modifying the original main prpgram. Part of the example is how to allocate the arrays: the example does that by having the subroutine that would first use the array test whether the array is allocated -- if not, it allocates the array.

Answer 2

The three examples below all work with gfortran. The second may fail on some compilers as it uses a F2003 feature (allocatable dummy arguments), and not all compilers are 100% F2003 compliant. However, most implement ISO TR 15581 (which includes this feature).
First version, you can use a common pointer to allocatable array.
program hip
implicit none
double precision, dimension(:, :), pointer :: p
common /hiphop/ p
double precision, allocatable, dimension(:, :), target :: a
allocate(a(100, 100))
a(1, 1) = 3.1416d0
p => a
call hop
deallocate(a)
end program
subroutine hop
implicit none
double precision, dimension(:, :), pointer :: p
common /hiphop/ p
print *, size(p, 1), size(p, 2), p(1, 1)
end subroutine
Second version, allocating in a subroutine then calling another. One still needs to declare the array in main program.
program hip
implicit none
interface
subroutine hip_alloc(arr)
double precision, allocatable, dimension(:, :) :: arr
end subroutine
end interface
double precision, dimension(:, :), pointer :: p
common /hiphop/ p
double precision, allocatable, dimension(:, :) :: a
p => null()
print *, "a:", allocated(a)
print *, "p:", associated(p)
call hip_alloc(a)
print *, "a:", allocated(a)
print *, "p:", associated(p)
call hop
deallocate(a)
end program
subroutine hip_alloc(arr)
implicit none
double precision, dimension(:, :), pointer :: p
common /hiphop/ p
double precision, allocatable, dimension(:, :), target :: arr
allocate(arr(100, 100))
arr(1, 1) = 3.1416d0
p => arr
end subroutine
subroutine hop
implicit none
double precision, dimension(:, :), pointer :: p
common /hiphop/ p
print *, size(p, 1), size(p, 2), p(1, 1)
end subroutine
Third version, here we first call a function returning a pointer, then pass this pointer to a subroutine through a common. The function does the allocation, as in second example. The pointer is deallocated in main program, but could be elsewhere.
program hip
implicit none
interface
function hip_alloc(n)
integer :: n
double precision, dimension(:, :), pointer :: hip_alloc
end function
end interface
double precision, dimension(:, :), pointer :: p
common /hiphop/ p
p => null()
print *, "p:", associated(p)
p => hip_alloc(100)
print *, "p:", associated(p)
call hop
deallocate(p)
end program
function hip_alloc(n)
implicit none
integer :: n
double precision, dimension(:, :), pointer :: hip_alloc
allocate(hip_alloc(n, n))
hip_alloc(1, 1) = 3.1416d0
end function
subroutine hop
implicit none
double precision, dimension(:, :), pointer :: p
common /hiphop/ p
print *, size(p, 1), size(p, 2), p(1, 1)
end subroutine

Answer 3

I do not understand why writing a MODULE would not work, but have you considered CONTAINS? Everything above the CONTAINS declaration is visible to the subroutines below the CONTAINS:
PROGRAM call_both
INTEGER,DIMENSION(2) :: a, b
a = 1
b = 2
PRINT *,"main sees", a, b
CALL subA
CALL subB
CONTAINS
SUBROUTINE subA
PRINT *,"subA sees",a,b
END SUBROUTINE subA
SUBROUTINE subB
PRINT *,"subB sees",a,b
END SUBROUTINE subB
END PROGRAM call_both
The output would be
main sees 1 1 2 2
subA sees 1 1 2 2
subB sees 1 1 2 2
This works with ALLOCATABLE arrays as well.