topic Re: saved the allocatables! in Software Archive

saved the allocatables!

rahzan — Thu, 20 Dec 2001 06:00:02 GMT

Normally the variables in a subroutine are saved from call to call. However, it seems that allocatables are not (and in fact automatically deallocated) upon exit from the subroutine. Is this true?

Here is the context I found this;

subroutine X_X !this happens to be a COM server method
call Y
...
call Y
....
end sub X_X

subroutine Y
real,allocatable:: A(:)
if(firsttime in Y) allocate(A)
call Z(A,sizeA)
end sub Y

subroutine Z(A,sizeA)
real A(sizeA)
...
end sub Z

On second call to Y and hence into Z, the server crashes as soon as anything in Z (or Y, I presume) refers to A. The problem goes away if I allocate and deallocate A every time Y is called.

Is this the correct behavior?

Tim

Re: saved the allocatables!

Steven_L_Intel1 — Thu, 20 Dec 2001 06:30:14 GMT

Yes, that is the correct behavior according to the standard. Please don't depend on implicit SAVE semantics for local variables - use SAVE if that's what you want. The only case where you can omit SAVE (but it doesn't hurt) is non-derived-type variables given an initial value through DATA or an initialization clause. (Derived type variables whose type specifies default initialization are NOT implicitly SAVEd, per the standard.)

Steve

Re: saved the allocatables!

rahzan — Thu, 20 Dec 2001 08:42:59 GMT

Hot diggity!
Took me 3 hours of fooling w/ it through access/vba tofind this out.

Thanks, Tim

Re: saved the allocatables!

Intel_C_Intel — Thu, 20 Dec 2001 18:06:30 GMT

I have a reverse problem. In most of my subroutines, the values are preserved between calls, although I don't bank on it. For one application however, I would like to start from scratch each time a subroutine is called. Is there any way of doing this other than resetting all the variables on input? I haven't yet found anything in the textbooks or help - I want a re-initialisation facility.

Bear of little brain

Re: saved the allocatables!

Steven_L_Intel1 — Fri, 21 Dec 2001 02:50:13 GMT

The only way to do this automatically is to make the variable be of derived type, where the type specifies default initialization. For example:


subroutine sub
type mytype
  integer :: i = 0
  end type mytype
type(mytype) localvar
...

Now each time the subroutine is entered, localvar%i will be reset to zero. Of course, it would be simpler to just add the initialization yourself!

Steve

Re: saved the allocatables!

rahzan — Fri, 21 Dec 2001 03:59:56 GMT

Bear,
Could it be that a PURE declaration do what you want?