topic Re: Problem with ReAlloc in Intel® Fortran Compiler

Problem with ReAlloc

davidgraham — Tue, 26 Apr 2005 20:16:36 GMT

I am trying to use the routine ReAllocbut I get the following error.

What am I doing wrong?

subroutine TryReAlloc

real,allocatable::B(:)
integer::j
real::c

c=1.34

do j=1,10
call ReAlloc (B,j)
B(j)=c*j
end do

end subroutine TryReAlloc

!--------------------------

subroutine ReAlloc (A,n)
! A array
! n new size

real,allocatable::A(:)
integer::n,nOld
real,allocatable::Temp(:)
nOld=size(A)
if (nOld > n) RETURN
allocate (Temp(nOld))
Temp=A
Deallocate (A)
Allocate (A(n))
A(1:nOld)=Temp
end subroutine ReAlloc

Warning: In the call to REALLOC, actual argument #1 does not match the type and kind of the corresponding dummy argument.
call ReAlloc (B,j)

Thanks,

David

Re: Problem with ReAlloc

Steven_L_Intel1 — Tue, 26 Apr 2005 20:41:20 GMT

You need an explicit interface to call a routine which has a deferred-shape (:) argument.

Re: Problem with ReAlloc

davidgraham — Wed, 27 Apr 2005 15:18:51 GMT

Thanks, I have got it working now.

I am trying to repicate the Visual Basic redim preserve command.

I have found that the method of using the ReAlloc routine takes long time for a large array.

Repeating the loop 100 time takes 0.000 secs, 1,000 times takes 0.08 secs, 10,000 times takes 8.4 secs, 100,000 times - I gave up waiting.

Is there a more efficient way of doing this?

David

Re: Problem with ReAlloc

Steven_L_Intel1 — Wed, 27 Apr 2005 19:51:12 GMT

Not at present. Fortran 2003 offers a way of doing a "realloc" on allocatables. You would have a bit better luck using POINTER as you could just move pointers around and just move the data once and not twice.

Re: Problem with ReAlloc

Jugoslav_Dujic — Thu, 28 Apr 2005 18:36:01 GMT

David,

You can speed it up using C code (or even, an equivalent Fortran code), by directly manipulating Fortran array descriptor. Basically, the F2000 MOVE_ALLOC does only one allocation instead of two, by means of having two pieces of allocated memory -- the old one and the new one -- simultaneously. Here's a sketch, which reusessome codefrom thread:

http://softwareforums.intel.com/ids/board/message?board.id=5&message.id=10361&view=by_date_ascending&page=1

Code:

void move_alloc(CVF_1D_DESCRIPTOR* A, int iSizeSingleElement,
  int iNewArraySize)
{
  void* lpOldAddress;
  lpOldAddress = A->lpAddress;
  A->lpAddress = malloc(iNewArraySize*iSizeSingleElement);

  // Copy the old contents into new location
  if (A->iAllocated) 
  {
     memcpy(lpOldAddress, A->lpAddress, A->Dim1.iExtent * iSizeSingleElement);
     // kill the old allocation
     free(lpOldAddress);
  }
  A->Dim1.iExtent = iNewArraySize;
  //Fill in the rest of A appropriately
}

Instead of malloc/memcpy/free you can use native Windows APIs or whatever. Note, however, that you have to use same allocators as were used to allocate the original array, meaning that you cannot e.g. free() memory which was not allocated with malloc() but e.g. with ALLOCATE (unless you happen to know which API is used by ALLOCATE internally). Thus, you should probably write your own (de)allocation routines in C, using the same malloc/free as used in move_alloc above.

Hope this helps,

Jugoslav

Re: Problem with ReAlloc

Steven_L_Intel1 — Thu, 28 Apr 2005 19:24:30 GMT

Hey, Jugoslav's back!

Re: Problem with ReAlloc

Jugoslav_Dujic — Thu, 28 Apr 2005 20:40:42 GMT

Alas, only temporarily :-( -- they merged some holidays so I got an extended weekend off. I'll be definitely back only in mid-August.

Regards

Jugoslav