Tree memory parameters and PMGRID size

From: Mark Baumann <markb_at_physics.utexas.edu>
Date: Thu, 11 Sep 2008 16:43:23 -0500 (CDT)

Hello Gadget users,

I would appreciate some advice on how to properly set the memory
allocation parameters in the parameter file. I receive errors along the
lines of "No domain decomposition that stays within memory bounds is
possible" or "maximum number of top-level nodes reached".

I've read through the User's Guide and the mailing list archive. I see
that the relevant parameters are probably PartAllocFactor and
TreeAllocFactor. Increasing these doesn't always seem to solve the
problem. Values for TreeAllocFactor ranging from 0.7 all the way to 1000
don't seem to fix the problem, whether I try a large run (several thousand
particles per processor) or a very small run (about 1 particle per
processor).

In general...

If you have a large # of particles per processor, what are recommended
values for PartAllocFactor and TreeAllocFactor?

On the opposite extreme, if you have a small # of particles per processor,
how should I set the allocation factors?


On a different note, about the size of the PM grid that is set by the
"PMGRID=###" compiler option... is that the size of the PM grid over the
entire computational volume, or is that the size of the PM grid per
processor? Also, is it the size of the PM grid in each dimension, or is
it the total number of grid cells? For the sake of a concrete example,
what would you recommended for a grid size for a system of 100,000
particles on 512 processors?

Thank you for your help!

Mark
Received on 2008-09-11 23:43:12

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