Re: [Meep-discuss] Parallel PyMeep - odd effect of resolution change

2017-12-19 Thread Ian Sage 

Thanks for your efforts on all our behalves, Ardavan.

Ian


On 19/12/2017 16:34, Ardavan Oskooi wrote:


This is a bug; the patch is on GitHub 
.




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Re: [Meep-discuss] Parallel PyMeep - odd effect of resolution change

2017-12-19 Thread Ardavan Oskooi 
This is a bug; the patch is on GitHub 
.


src/susceptibility.cpp: 160

-   return b*b > c && 2*b*b - c + 2*fabs(b)*sqrt(b*b - c) > 1;
+  return b*b > c && float(2*b*b - c + 2*fabs(b)*sqrt(b*b - c)) > 1;

On 12/18/2017 05:27 AM, Ian Sage wrote:

In trying to educate myself about Meep and FDTD, I have been running
various toy simulations, and most recently have tried to replicate metal
reflectivity results as presented at

http://juluribk.com/2011/04/27/plasmonic-materials-in-meep/ ;

the project file linked from that page is also the source of the LD
model parameters I have used. I am using the github source of Dec 8th
commits, on Arch Linux.

According to the value of resolution I choose, the simulation may
succeed or fail with a message such as: "meep: Lorentzian pole at too
high a frequency 1e-20 for stability with dt = 0.00125313: reduce the
Courant factor, increase the resolution, or use a different dielectric
model" but the pattern of success/failure bewilders me. For example:

resolution (set in run_parameters.py)
50 - succeeds
100 - fails
150 - succeeds
200 - succeeds
300 - fails
350 - succeeds
400 - fails
401 - succeeds
399 - fails
398 - succeeds

When the simulation succeeds, the results closely match those in the
source reference and are almost superimposable apart from the
resolution=50 run. I think the simulation files are pretty simple -
attached.

Am I doing something fundamentally wrong - or is there a rational
explanation, or bug?

Many thanks,

Ian
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[Meep-discuss] Parallel PyMeep - odd effect of resolution change

2017-12-18 Thread Ian Sage 
In trying to educate myself about Meep and FDTD, I have been running
various toy simulations, and most recently have tried to replicate metal
reflectivity results as presented at

http://juluribk.com/2011/04/27/plasmonic-materials-in-meep/ ;

the project file linked from that page is also the source of the LD
model parameters I have used. I am using the github source of Dec 8th
commits, on Arch Linux.

According to the value of resolution I choose, the simulation may
succeed or fail with a message such as: "meep: Lorentzian pole at too
high a frequency 1e-20 for stability with dt = 0.00125313: reduce the
Courant factor, increase the resolution, or use a different dielectric
model" but the pattern of success/failure bewilders me. For example:

resolution (set in run_parameters.py)
50 - succeeds
100 - fails
150 - succeeds
200 - succeeds
300 - fails
350 - succeeds
400 - fails
401 - succeeds
399 - fails
398 - succeeds

When the simulation succeeds, the results closely match those in the
source reference and are almost superimposable apart from the
resolution=50 run. I think the simulation files are pretty simple -
attached.

Am I doing something fundamentally wrong - or is there a rational
explanation, or bug?

Many thanks,

Ian



metal_mirror.sh
Description: application/shellscript
import meep as mp
import metals
from run_parameters import *

#k_point=mp.Vector3(0,0,0)
#sym = mp.Mirror(direction=mp.Y, phase=1)

cell=mp.Vector3(x_size, y_size)

sources = [mp.Source(mp.GaussianSource(fcen, fwidth=df),
 component=mp.Ez,
 center=mp.Vector3(0, source_y),
 size=mp.Vector3(x_size, 0))]

pml_layers=[mp.PML(pmld)]

sim=mp.Simulation(cell_size=cell,
  boundary_layers=pml_layers,
  #geometry=geometry,
  sources=sources,
  #symmetries=[sym],
  resolution=resolution)

refl_fr = mp.FluxRegion(center=mp.Vector3(0, fr_y), size=mp.Vector3(x_size/2-pmld, 0))

#pt=mp.Vector3(0, 0)

refl = sim.add_flux(fcen, df, nfreq, refl_fr)

sim.run(mp.at_beginning(mp.output_epsilon),
mp.to_appended("ez", mp.at_every(0.1, mp.output_efield_z)),
until=sim_duration)

sim.save_flux('refl-flux', refl)
sim.display_fluxes(refl)
import meep as mp
import metals
from run_parameters import *

cell=mp.Vector3(x_size, y_size)

sources = [mp.Source(mp.GaussianSource(fcen, fwidth=df),
 component=mp.Ez,
 center=mp.Vector3(0, source_y),
 size=mp.Vector3(x_size, 0))]

geometry=[mp.Block(mp.Vector3(x_size, metal_thickness, 1e20),
   center=mp.Vector3(0, metal_y),
   material=metals.silver)]

pml_layers=[mp.PML(pmld)]

sim=mp.Simulation(cell_size=cell,
  boundary_layers=pml_layers,
  geometry=geometry,
  sources=sources,
  resolution=resolution)

refl_fr = mp.FluxRegion(center=mp.Vector3(0, fr_y), size=mp.Vector3(x_size/2-pmld, 0))

#pt=mp.Vector3(0, 0)

refl = sim.add_flux(fcen, df, nfreq, refl_fr)

sim.load_minus_flux('refl-flux', refl)

sim.run(mp.at_beginning(mp.output_epsilon),
mp.to_appended("ez", mp.at_every(0.1, mp.output_efield_z)),
until=sim_duration)

sim.display_fluxes(refl)
import meep as mp

susc_aluminium = [
mp.LorentzianSusceptibility(frequency=8.06e-21, gamma=0.0379, sigma=1.173e42),
mp.LorentzianSusceptibility(frequency=0.13066, gamma=0.2686, sigma=1940.97)
]

susc_silver = [
mp.LorentzianSusceptibility(frequency=1e-20, gamma=0.038715, sigma=4.4625e41),
mp.LorentzianSusceptibility(frequency=0.65815, gamma=3.1343, sigma=7.9247),
mp.LorentzianSusceptibility(frequency=3.6142, gamma=0.36456, sigma=0.50133),
mp.LorentzianSusceptibility(frequency=6.6017, gamma=0.052426, sigma=0.013329),
mp.LorentzianSusceptibility(frequency=7.3259, gamma=0.7388, sigma=0.82655),
mp.LorentzianSusceptibility(frequency=16.365, gamma=1.9511, sigma=1.1133)
]

silver = mp.Medium(epsilon=1.0, E_susceptibilities=susc_silver)
x_size=.6
y_size=.5
pmld=.10
metal_thickness=.1
sim_duration=11

fcen = 3.333
df = 3.0

source_y=-y_size/2+1.5*pmld
metal_y=y_size/2-metal_thickness/2-1.5*pmld
fr_y=((y_size/2-1.5*pmld-metal_thickness)+(1.5*pmld-y_size/2))/2

nfreq=250

resolution=398

if __name__=="__main__":
print("Simulation space from Y = ", -y_size/2, " to Y = ", y_size/2)
print("Source position = ", source_y)
print("Metal position = ", metal_y, " from ", metal_y-metal_thickness/2, " to ", metal_y+metal_thickness/2)
print("Flux measured at = ", fr_y)
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