| Re: yet another idl memory question [message #66691 is a reply to message #66689] |
Thu, 04 June 2009 09:29   |
Jean H.
Messages: 472
Registered: July 2006
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Senior Member |
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Hi,
Unless you are using pointers, you can not be sure that the same memory
space will be used in the different function calls.... and you don't
really have to care either, especially under Linux.
If you do the same processing on data of the same size, it is likely
because your code is using memory and not releasing it. Two things come
to mind: 1) you are creating a pointer but never destroy it and 2) you
are saving your results... in which case you may want to save the
variable(s) to a file, free the memory (data=0B) and start processing
the next file.
Jean
jw2519@columbia.edu wrote:
> How do I force that IDL set aside a chunk of contiguous memory to be
> refilled by a variable of equal size at each iteration of a procedure?
>
> More specifically, I have a code which consists of three procedures.
> One of these serves as the wrapper, one uses the IDL OpenDAP utility
> to download the relevant data, and the third processes the data into
> the grid and format that I want. The code will iterate for as long as
> the wrapper indicates that processed data files need to be created. I
> am running this on a 64-bit linux machine (IDL 7.0).
>
> Each iteration of the code performs four OpenDAP calls; each call
> downloads a large (~750MB) structure. After several iterations, the
> code exits with an insufficient memory to allocate array error (or
> sometimes "error reading value array: read is for xxx bytes, but there
> are only yyy in the buffer"; always this error occurs within an
> OpenDAP call). Using help,/memory and several of the tricks and tools
> posted elsewhere, I have been able to substantially reduce the max
> memory usage, but this only nets me another one and a half iterations
> or so. So my guess is that the problem is that there is no longer a
> sufficiently large block of contiguous memory into which to download
> the structure. Each of the four structures is of equal size at each
> iteration. How can I set aside a block of contiguous memory so that
> IDL will reuse the same chunk for each structure every time i call the
> procedure? I've tried using a solitary common block (i.e. just within
> the procedure in question), and I've attempted to use pointers. The
> program runs in both cases, but still exits with the same error. Of
> course, I am not at all certain that I used either of these
> correctly...
>
> Any suggestions are greatly appreciated.
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