CODEWITHSUNDEEP
fortrangfortran
user4372504
user4372504

Reputation:

Memory allocation and deallocation in separate module

This is my code:

Program Dynamic_Array

Use Variables
Use Allocation_Module
Use Dealloaction_Module

Implicit none

Call Subroutine_0

Call Subroutine_1

End Program Dynamic_Array

Module Variables

Implicit none

Integer :: i , k
Integer , parameter :: Br_sn_cvo = 10
Integer , parameter :: Br_nn_mre = 7
Integer , parameter , dimension ( Br_nn_mre) :: Br_nn_cvo = [ 7 , 6 , 5 , 4 , 3 , 2 , 1 ]
Integer , dimension ( Br_nn_mre ) :: i_nn_dm_1 , i_nn_dm_2

type :: my_type

     integer, allocatable :: my_size(:)

end type my_type

type(my_type), allocatable :: dS_sn(:)

End Module Variables

Module Allocation_Module

Use Variables

Implicit none

Contains

Subroutine Subroutine_0

Allocate(dS_sn(Br_nn_mre))

Loop_1: Do k = 1, Br_nn_mre

        i_nn_dm_1(k) = Br_sn_cvo + Br_nn_mre + 1 + Br_nn_cvo(k) * ( k - 1 )
        i_nn_dm_2(k) = Br_sn_cvo + Br_nn_mre + k * Br_nn_cvo(k)

        Allocate( dS_sn(k)%my_size( i_nn_dm_1(k) : i_nn_dm_2(k)) )

        Loop_2: Do i = i_nn_dm_1(k) , i_nn_dm_2(k)

                   dS_sn(k)%my_size(i) = i + k

                End Do Loop_2

        End do loop_1

End subroutine Subroutine_0

End Module Allocation_Module

Module Dealloaction_Module

Use Variables

Implicit none

Contains

Subroutine Subroutine_1

Do k = 1 , Br_nn_mre

   Deallocate(dS_sn(k)%my_size)

End do

   Deallocate(dS_sn)

Return
End Subroutine Subroutine_1

End Module Dealloaction_Module

I am not experienced programer in Fortran so I need to ask a few questions about process of memory allocation and deallocation for a dynamic arrays. Is there any problem with memory leak in this code? Is this correct way for a memory allocation in separate module? Is this correct way for a memory deallocation in separate module?

Upvotes: 0

Views: 946

Answers (2)

Holmz
Holmz

Reputation: 724

Here is an example...

...

IF(ALLOCATED(TheArray)) THEN
  IF(SIZE(TheArray) /= The_Size_I_need) DEALLOCATE(TheArray)
ENDIF
IF(.NOT.  ALLOCATED(TheArray)) ALLOCATE(TheArray(The_Size_I_need))

This is useful if the array gets used repeatedly for different processing sizes.

If it is "always" fixed in terms of the current execution, then there is no real need to do anything.

Upvotes: 1

Vladimir F Героям слава
Vladimir F Героям слава

Reputation: 60008

There is no memory leak in the code. It is impossible to make a memory leak with allocatable entities in Fortran. Only pointer can cause a memory leak.

With allocatable if something is going out of scope, it is deallocated automatically.

Your main array is a module variable so it is never going out of scope (it is save implicitly by Fortran 2008 rules). So if you don't deallocate it yourself, it will remain allocated and then deleted by the operating system on the program termination. But that is not normally considered to be a memory leak. It is not really harmful, because there is no way to make some forgotten copies of the array in memory.

The individual components my_size could go out of scope, when deallocating the large array dS_sn. In that case they are deallocated automatically by Fortran rules. You don't have to deallocate them one by one.

So you do not really have to do

Do k = 1 , Br_nn_mre

   Deallocate(dS_sn(k)%my_size)

End do

Doing just

Deallocate(dS_sn)

is perfectly correct.

Upvotes: 0

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