Re: [Meep-discuss] Meep-mpi: hard limit of ~ 2e9 points?
Hello, While it is good to see that many users are interested in adaptive resolutions for meep, what I meant was actually Is there any interest *by the developers* to implement such a feature somewhen?. Mischa wrote: you could consider doing a coordinate transformation that magnifies the region that you are interested in, and compensate for that by choosing an appropriately modified epsilon profile: http://www.mail-archive.com/meep-discuss@ab-initio.mit.edu/msg03029.html The exploit of scaling of Maxwell's Equations which you suggest is very interesting, I hadn't thought about that! Would it also work with the current implementation of dispersive materials? (Since only the \sigma can be a function of position?) gpipc wrote: what resolution you need? I am not yet sure I am finished with the convergence study. Right now it looks like this: My nanostructure has a characteristic radius of curvature of ~ 50 nm, but is much larger than that (um range). Since I'm only interested in an estimate of the effects of beam propagation near the structure, I obtain reasonable looking results for quite coarse resolutions of ~ 12.5 nm. The maximum I can afford is ~ 4 nm, calculating on a cluster, with a simulation box of ~ 5*5*3 um and dispersive materials. I get decent results for a 20 nm diameter nanosphere in two dimensions (so it is actually a cylinder) with 0.5 nm resolution, but they do not seem to be enough for 3d (I am trying a calculation with 0.25 nm resolution now). I compare the FDTD scattering efficiencies with Mie theory. I would think needing a better resolution for 3d than for 2d is the intuitive result, no? I personally would be extremely careful with such high resolutions. At 0.25 nm you are in the range where you have a single atom per pixel/voxel. Maxwell's Equations (in matter) are a macroscopic theory formulated for fields which should be considered averaged over many atom distances. I would not expect any classical electromagnetic theory to accurately describe experiments on this length scale. Georg On Wed, Dec 29, 2010 at 1:02 PM, gpipc gp...@cup.uni-muenchen.de wrote: On Wed, 29 Dec 2010 01:36:54 +0100, Georg Wachter georgwach...@gmail.com wrote: PS.: I would really like to see a possibility for having regions of different resolution in meep. This is The One Feature (for me) that commercial competitors have over Meep or any free electromagnetism software. Is there any interest that this might be implemented soonishly? I, for one, would be interested. But I must admit that I do not have any clue on how much effort it could cost developers to code this. -- Giovanni Piredda Postdoc - AK Hartschuh Phone: ++49 - (0) 89/2180-77601 Fax.: ++49 – (0) 89/2180-77188 Room: E2.062 Message sent by Cup Webmail (Roundcube) ___ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
Re: [Meep-discuss] Meep-mpi: hard limit of ~ 2e9 points?
On Wed, 29 Dec 2010 01:36:54 +0100, Georg Wachter georgwach...@gmail.com wrote: Hello, For the simulation of small metal structures with meep, I unfortunately need a ridiculously high resolution, Hi Georg, since we are working with a similar FDTD problem (simulation of small metal structures) and the same program - Meep - would you mind telling a bit more precisely what resolution you need? I am doing some experimentation with scattering from a nanosphere and I have got the impression that simulating accurately a *spectrally* sharper resonance one needs a higher *spatial* resolution, does this make any sense? The only bit of information that I have at the moment regarding this is that if in a Drude model for a metal I decrease the damping, then I need a better spatial resolution to simulate with the same accuracy the scattering at the plasmon resonance. I haven't yet tried with structures different from a sphere. Also, I have noticed that for the same model of the metal (same Drude- Lorentz parameters) a 3d simulation requires higher resolution than a 2d simulation. Right now I get decent results for a 20 nm diameter nanosphere in two dimensions (so it is actually a cylinder) with 0.5 nm resolution, but they do not seem to be enough for 3d (I am trying a calculation with 0.25 nm resolution now). I compare the FDTD scattering efficiencies with Mie theory. The point of all of this is figuring out what is the coarsest resolution which gives decent results, and doing the actual simulations with that. Giovanni -- Giovanni Piredda Postdoc - AK Hartschuh Phone: ++49 - (0) 89/2180-77601 Fax.: ++49 – (0) 89/2180-77188 Room: E2.062 Message sent by Cup Webmail (Roundcube) ___ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
Re: [Meep-discuss] Meep-mpi: hard limit of ~ 2e9 points?
On Wed, 29 Dec 2010 01:36:54 +0100, Georg Wachter georgwach...@gmail.com wrote: PS.: I would really like to see a possibility for having regions of different resolution in meep. This is The One Feature (for me) that commercial competitors have over Meep or any free electromagnetism software. Is there any interest that this might be implemented soonishly? I, for one, would be interested. But I must admit that I do not have any clue on how much effort it could cost developers to code this. -- Giovanni Piredda Postdoc - AK Hartschuh Phone: ++49 - (0) 89/2180-77601 Fax.: ++49 – (0) 89/2180-77188 Room: E2.062 Message sent by Cup Webmail (Roundcube) ___ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
[Meep-discuss] Meep-mpi: hard limit of ~ 2e9 points?
Hello, For the simulation of small metal structures with meep, I unfortunately need a ridiculously high resolution, leading to a lot of points in my simulation box (around 2.2e9). On trying to run a 512-core job, I ran into a strange error: meep_highres.e489139:meep: Cannot split -2080123546 grid points into 512 parts In the source code, it says [structure.cpp - void structure::check_chunks() ]: // FIXME: should use 'long long' else will fail if grid 2e9 points So it appears to be due to the range of the integer variable. Is this an easy fix, or does it have side effects? (You can tell that I'm a FORTRAN user.) Best regards, Georg PS.: I would really like to see a possibility for having regions of different resolution in meep. This is The One Feature (for me) that commercial competitors have over Meep or any free electromagnetism software. Is there any interest that this might be implemented soonishly? ___ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
