Re: [ESPResSo-users] activate magnetostatics method DipolarDirectSumCpu

[Rudolf Weeber]

Hi,
On Fri, May 10, 2019 at 09:05:12PM +0800, address@hidden wrote:
> I think the DipolarDirectSumCpu is a long range interaction and the command 
> of mpi version will divide the whole box into local boxes so that each node 
> sees everything on its own local box and on one layer of cells. Due to that, 
> the DipolarDirectSumCpu can't work fine! Is that why I could not activate 
> magnetostatics method DipolarDirectSumCpu with the command of mpi version? If 
> it's true, how can I calculate the dipolar interaction with open boundary?
The dipolar direct sum on th CPU is not parallelized. You can only use it on a 
single core.
The remaining simulation is typically suited for a single cpu core.

There is a gpu implementation (DipolarDirectSumGpu) optimized for systems with 
more than ~2000 magnetic particles.
For large systems (>~10000 dipoles), you can use the P2NFFT method
https://www.sciencedirect.com/science/article/pii/S0021999119301020
It scales as N log N in the number of dipoles (as opposed to N^2 for direct 
summatoin). The supplementary information contains usage examples for ESPResSo.

Hope that helps!
Regards, Rudolf