|Subject:||Re: [ESPResSo-users] minimum number of cells|
|Date:||Thu, 17 Jul 2014 14:23:47 -0400|
Yes, it's an error, not warning, for "number of cells is smaller than minimum". The simulation box sizes are 20, 20 and 19 and each side is larger than twice the r_cut. P3M parameters are from automatic tuning.
It requires at least 2 cells per spatial dimension, then "min_num_cells" is 8 on 1 core, and it's 1 on 8 cores. For 16 cores, if I set min_num_cells to 1, for the whole system, the total min_num_cells is 1*16=16 and it's safe for the simulation, is my understanding correct?
Thank you four your time and help.
Date: Wed, 16 Jul 2014 22:12:01 +0200
To: address@hidden; address@hidden
Subject: Re: [ESPResSo-users] minimum number of cells
On 16.07.14 18:59, Xikai Jiang wrote:
You don't get a warning, but an error message, since Espresso would produce incorrect results. We need at least two cells per spatial dimension to make the minimum image convention unambiguous. minimum_num_cells however counts per core, so if you have 2 cores, you just need 4, and for 4 cores 2.
No, first of all you cannot set minimum_num_cells to a lower value, since ESPResSo wants to avoid computing incorrect results. As a consequence, there is a limit to the cutoff depending on the box size. You simply cannot use r_cut 3.3 in a box smaller than 6.7. Either, you put more particles to increase the box size, or you don't insist on your parameters, but rather let P3M tune them.
-- JP Dr. Axel Arnold ICP, Universität Stuttgart Allmandring 3 70569 Stuttgart, Germany Email: address@hidden Tel: +49 711 685 67609
|[Prev in Thread]||Current Thread||[Next in Thread]|