| Re: Common block compilation error [message #73660] |
Tue, 23 November 2010 07:49 |
Jeremy Bailin
Messages: 618
Registered: April 2008
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Senior Member |
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On Nov 22, 9:00 am, Gray <grayliketheco...@gmail.com> wrote:
> Hi all,
>
> I'm using the NASA IDL astronomy library's MINF_BRACKET and
> MINF_PARABOLIC routines to minimize a function. Doing so requires
> that I use a common block for some other parameters. The routine that
> calls the minimization routines gets passed the parameters and stores
> them in the common block. I had thought that I could name the input
> parameters for the calling function as the same as the common block
> variables, so that they would be automatically stored, but doing so
> gives a compilation error, and so I have to name them differently and
> assign their values to the common block variables. Is there any
> reason why this should be so? It seems an unnecessary extra step...
>
> --Gray
>
> Code (gives error):
>
> FUNCTION m87_scl, scl
> common m87scal, img, im0
> return, robust_sigma(img*scl-im0,/zero)
> end
>
> FUNCTION m87_scale, img, im0
> common m87scal
> xa = 0.1 & xb = 10.
> minf_bracket, xa, xb, xc, func_name='m87_scl'
> minf_parabolic, xa, xb, xc, scl, func_name='m87_scl'
> return, scl
> end
The problem is that it doesn't know about the common block in the
function definition, so it creates variables named "img" and "im0"
that are not part of the common block... and then when you tell it
that you want variables of the same name that are part of a common
block, it complains that it already has variables with those names
that are using their own memory.
If they weren't being passed in as function arguments, it's easy, but
since they are I don't see any easy way around it. If the problem is
that those are huge and you're walloping tons of memory by having two
copies of them, you could try passing pointers instead, so you just
need to make copies of the pointers, and then dereference them inside
m87_scl.
-Jeremy.
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