Recursion limitations

[hgr_iwf]

Hello!

Are there limitations by calling recursive subroutines?

I tried the following very simple program and after 18421 times of calling the routine I got an error message.

Code:
-------
(main program)

implicit none
integer(2) :: n
n = 1
write(*,*) 'begin'
call factorial(n)
END

(recursive subroutine)
RECURSIVE SUBROUTINE factorial (n)
integer(2), intent(inout) :: n
write(*,*) 'n: ', n
n = n + 1
call factorial (n)
END SUBROUTINE

Error message:
------------------
Unhandled exception at 0x7d61f448 in test.exe: 0xC0000005: Access violation writing location 0x00030e3c.
There is no source code available for the current location.

Thanks for your help,
Hannes

[GVautier]

Quoting - hgr_iwf

Hello!

Are there limitations by calling recursive subroutines?

I tried the following very simple program and after 18421 times of calling the routine I got an error message.

Code:
-------
(main program)

implicit none
integer(2) :: n
n = 1
write(*,*) 'begin'
call factorial(n)
END

(recursive subroutine)
RECURSIVE SUBROUTINE factorial (n)
integer(2), intent(inout) :: n
write(*,*) 'n: ', n
n = n + 1
call factorial (n)
END SUBROUTINE

Error message:
------------------
Unhandled exception at 0x7d61f448 in test.exe: 0xC0000005: Access violation writing location 0x00030e3c.
There is no source code available for the current location.

Thanks for your help,
Hannes

Hello

When you call a recursive function, it takes space in the stack at each call (in your case dont forget that "write" use stack space). So it comes a point where the stack is full.

In your case, you don't have exit condition so it cannot ends. So the program will crash on stack overflow or integer overflow when "n" will reach 2^31.

[TimP]

Quoting - gvautier

Hello

When you call a recursive function, it takes space in the stack at each call (in your case dont forget that "write" use stack space). So it comes a point where the stack is full.

In your case, you don't have exit condition so it cannot ends. So the program will crash on stack overflow or integer overflow when "n" will reach 2^31.

n was declared with KIND=2, so bad things should happen much sooner than that.