Thank you very much for the help. I read the part of the manual you referred to, it is now clear how to choose the decomposition.<div>Cheers</div><div>Paolo<br><br><div class="gmail_quote">On 3 April 2012 17:16, Mark Abraham <span dir="ltr"><<a href="mailto:Mark.Abraham@anu.edu.au">Mark.Abraham@anu.edu.au</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="im">On 3/04/2012 11:58 PM, Paolo Franz wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hello!<br>
I am wondering if the domain decomposition chosen by the code, once the number of cpus dedicated to PME is chosen,can be overridden somehow. That is, if in some sort there exist a reciprocal space equivalent of "-dd" for the domain decomposition of the direct space. The problem I have is that I am trying to get a good scaling factor for some large system I have, on 1000/2000 CPUs. If for instance I have 128 CPU on PME and a 128^3 grid, I would like to have a decomposition 8X16X1 on PME, which should be perfectly ok with the parallelization scheme, if I understand it correctly. Unfortunately, the default one I get is 128X1X1, which is inevitably very inefficient. Is there anything I could be doing?<br>
</blockquote>
<br></div>
The automatic choice depends on a large number of factors. A big factor is optimizing the PP<->PME communication load. Big common factors in the divisions of processors into grids are key, so long as those factors can lead to useful hardware mappings. In particular, see last para 3.17.5 of manual.<span class="HOEnZb"><font color="#888888"><br>
<br>
Mark<br>
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