Segmentation fault for 3D simulation using 1D cell

[oskooi]

I am running into an unexpected segmentation fault when trying to run a 3D simulation using a 1D cell. This only occurs for certain grid resolutions and Bloch-periodic boundary conditions.

This issue can be reproduced using the script below which involves a point source in vacuum with Bloch-periodic boundaries in $x$ and $y$ (k_point = (-0.2, -0.2, 0)). The simulation is fine when RESOLUTION_UM is 51 but produces the segfault for values of 52 and 53. Changing the k_point also runs fine (no segfault).

The problem therefore seems to be some combination of the grid resolution and the Bloch-periodic boundaries for a 1D cell. I should also mention that I am using Meep compiled using single-precision floating point and OpenMP.

Case 1: RESOLUTION_UM = 51

Initializing structure...
time for choose_chunkdivision = 7.7198e-05 s
Working in 3D dimensions.
Computational cell is 0.0196078 x 0.0196078 x 12 with resolution 51
time for set_epsilon = 0.00449374 s
-----------
Meep: using complex fields.
field decay(t = 50.009803921568626): 0.2511579661675122 / 0.2511579661675122 = 1.0
field decay(t = 100.01960784313725): 0.25115618711643334 / 0.2511579661675122 = 0.9999929166050117
field decay(t = 150.02941176470588): 1.7969355984235213e-10 / 0.2511579661675122 = 7.154603239719811e-10
run 0 finished at t = 150.02941176470588 (15303 timesteps)

Elapsed run time = 2.3554 s

Case 2: RESOLUTION_UM = 52

Using MPI version 3.1, 1 processes
-----------
Initializing structure...
time for choose_chunkdivision = 9.0651e-05 s
Working in 3D dimensions.
Computational cell is 0.0192308 x 0.0192308 x 12 with resolution 52
time for set_epsilon = 0.00381082 s
-----------
Meep: using complex fields.
[devbig095:2604209:0:2604209] Caught signal 11 (Segmentation fault: address not mapped to object at address (nil))
==== backtrace (tid:2604209) ====
 0  /lib64/libucs.so.0(ucs_handle_error+0x2e4) [0x7ff45fc81e44]
 1  /lib64/libucs.so.0(+0x2a4cd) [0x7ff45fc834cd]
 2  /lib64/libucs.so.0(+0x2a6aa) [0x7ff45fc836aa]
 3  /home/oskooi/install/meep/src/.libs/libmeep.so.33(_ZN4meep6fields15step_boundariesENS_10field_typeE+0x4b4) [0x7ff465a314c4]
=================================
[devbig095:2604209] *** Process received signal ***
[devbig095:2604209] Signal: Segmentation fault (11)

import meep as mp
import numpy as np

RESOLUTION_UM = 51
WAVELENGTH_UM = 1.0

frequency = 1 / WAVELENGTH_UM
pml_um = 1.0
air_um = 10.0
size_z_um = pml_um + air_um + pml_um
cell_size = mp.Vector3(0, 0, size_z_um)

pml_layers = [mp.PML(thickness=pml_um)]

src_cmpt = mp.Ex

k_point = mp.Vector3(-0.2, -0.2, 0)

sources = [
    mp.Source(
        src=mp.GaussianSource(frequency, fwidth=0.1 * frequency),
        component=src_cmpt,
        center=mp.Vector3()
    )
]

sim = mp.Simulation(
    resolution=RESOLUTION_UM,
    force_complex_fields=True,
    cell_size=cell_size,
    sources=sources,
    boundary_layers=pml_layers,
    k_point=k_point
)

sim.run(
    until_after_sources=mp.stop_when_fields_decayed(
        50, src_cmpt, mp.Vector3(), 1e-6
    )
)