Open GoogleCodeExporter opened 8 years ago
Original comment by yurkin
on 7 Jun 2010 at 6:12
Concerning the Fast Multipole Method (FMM), there are some important things to
keep in mind. Application of FMM for the DDA is very poorly studied, however
some insights can be obtained from literature on FMM applied to
surface-integral equation (which now keeps the world record in simulated size
of particles about 400 wavelengths).
There are two versions of FMM - single-level and multilevel, which scale as
N^1.5 and N*logN respectively (N - number of dipoles). The standard FFT-DDA
scales as N*logN (with a lower prefactor), so multilevel FMM seems to be a nice
option for porous particles, etc. The problem is that multilevel FMM is very
complex by itself, and almost impossible to effectively parallelize for larger
than 16 or 32 cores. Single-level FMM can be effectively parallelized up to
1024 cores and beyond, but its scaling is less favorable.
So for applications involving large particles and large computer clusters, the
boundary between suitability of standard FFT-DDA and FMM (single-level
remaining the only option) shifts to more porous particles. However, there are
definitely some applications where even single-level FMM can be superior.
Consider, e.g., a fractal aggregate with a large number of monomers n=O(R^Df),
where R is outer radius, and Df is fractal dimension. Then standard FFT-DDA
scales as O(R^3)=O[n^(3/Df)] and single-level FMM - as O(n^1.5). So for Df<2
(which is often the case is real applications) FMM will be better.
Original comment by yurkin
on 3 Dec 2010 at 4:53
Development of sparse (non-FFT) implementation of the DDA was started (some
time ago) by Jussi Leinonen on a branch 'sparse' -
http://code.google.com/p/a-dda/source/browse/#svn/branches/sparse . See r1078 -
r1080.
Original comment by yurkin
on 4 Jun 2012 at 3:58
[deleted comment]
[deleted comment]
The sparse mode is now included as an experimental feature. See
http://code.google.com/p/a-dda/wiki/UsingADDAInSparseMode for more information.
Original comment by jsleino...@gmail.com
on 22 Nov 2012 at 10:38
The wiki page, mentioned in previous comment was renamed to SparseMode.
The next big thing for the sparse mode is the GPU acceleration, using OpenCL.
Since FFT is not used in sparse mode, the potential of acceleration is even
greater than for the standard mode.
Original comment by yurkin
on 31 Jan 2013 at 7:00
Another interesting idea is to enable storing of interaction matrix (through a
command line option). This will accelerate computations (at least for
non-trivial interaction methods) at the expense of a lot of memory. This may be
relevant in some cases. Moreover, it can be controlled by command line option
'-opt {speed|mem}'.
Original comment by yurkin
on 4 Feb 2013 at 6:02
Original comment by yurkin
on 2 Jul 2014 at 8:41
Original issue reported on code.google.com by
yurkin
on 7 Jun 2010 at 6:11