[gradsusr] optimization of memory in grads, use undefine

[Muhammad Yunus Ahmad Mazuki]

You could use undefine to free memory allocated to variable that you dont
need anymore. Say you had A=5. Then you compute B=6*A. Then C=A*B. Each of
this simple step would have certain memory allocated to A, B and C. This is
simple variables, that means the memory allocated is small. But if A to C
were to contain any of your file parameter such as temperature, the
allocated memory will be larger. So by the time you have computed C, and
you no longer needed A and B in further computation, you can use 'undefine
A' and 'undefine B'. The emory allocated to A and B will be freed for you
to use on other computation. How is your script actually is? Have you try
to optimise your script? You can check
http://www.iges.org/grads/gadoc/variable.html . Another part is to limit
the size of your defined variable (A to C). For example:
set lat 0 90
set lon 0 360
set lev 300 850
set t 1 100
define A=temp
This would assign A to have temperature data from 0 to 90 Latitude, 0-360
latitude, 300-850 (I usually use geopotential height) and from t of 1-10.
But do you need all of it to be in the variable A? Perhaps you had only
need lat of 0-20 and longitude of 20-40. And further computation of A
definitely only need lat of 0-20 and longitude of 20-40, in this case you
had given unneeded memory allocation to A. Which if you repeat with other
defined variables and calculations, the used memory will just build up, and
you will run out allocated memory soon. You can try these two method first.

Yunus

On Mon, Dec 17, 2012 at 8:13 PM, Isaac Pozo <ipozo at mncn.csic.es> wrote:

> Hi, this is my first post to the grads list. I'm a biologist that has
> been working with grads for the last months, but now I'm facing memory
> problems.
>
>
> I'm trying to run a  script with 43825 times and seven variables.
>
> I'm doing a series of arithmetical functions in between the variables,
> and generating more variables.
>
> And I'm constantly getting memory dumps. "Unable to allocate data
> memory" "Size of request was 946620000 grid elements"
>
> So apart of finding a good RAM computer, (I'm working in a 8 GB ram WK
> and have problems) I was wondering if somebody can guide me through
> documentation and tricks on how to optimize the scrip to save RAM.
>
> I also have access to supercomputation and CUDA machines, does anyone
> have worked with this type of systems in GRADS
>
> Thanks in advance  for your help
>
>
>
>
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