FourierFields in cylindrical coordinates error

[ejohlin]

Trying to use the FourierFields adjoint objective when the simulation is in 2D cylindrical coordinates returns an error with respect to the volume argument passed to FourierFields. This was found by modifying the example Adjoint FarField code to use cylindrical coordinates (which runs fine), and then try to change the objective to use FourierFields (which then fails).

Trying to call FourierFields with cylindrical coordinates returns the following error for the Volume (abbreviated):

ValueError                                Traceback (most recent call last)
File ~/miniconda3/envs/mp/lib/python3.10/site-packages/meep/adjoint/objective.py:237, in FourierFields.__init__(self, sim, volume, component, yee_grid, decimation_factor)
    235 def __init__(self, sim, volume, component, yee_grid=False, decimation_factor=0):
    236     super().__init__(sim)
--> 237     self.volume = sim._fit_volume_to_simulation(volume)
    238     self.component = component
    239     self.yee_grid = yee_grid

File ~/miniconda3/envs/mp/lib/python3.10/site-packages/meep/simulation.py:1275, in Simulation._fit_volume_to_simulation(self, vol)
   1274 def _fit_volume_to_simulation(self, vol):
-> 1275     return Volume(vol.center, vol.size, dims=self.dimensions, is_cylindrical=self.is_cylindrical)

File ~/miniconda3/envs/mp/lib/python3.10/site-packages/meep/simulation.py:393, in Volume.__init__(self, center, size, dims, is_cylindrical, vertices)
...
    103     return mp.vec(v3.x, v3.y, v3.z)
    104 else:
--> 105     raise ValueError("Invalid dimensions in Volume: {}".format(dims))

ValueError: Invalid dimensions in Volume: -2

I could not find the reason for the volume dimension to be set to -2.

A MWE for reproducing:

import meep as mp
import meep.adjoint as mpa
pml_layers = [mp.PML(1.0)]
sim = mp.Simulation(
    cell_size=mp.Vector3(3, 0, 3),
    boundary_layers=pml_layers,
    dimensions=mp.CYLINDRICAL,
    m=0,
    default_material=mp.Medium(index=1.0),
    resolution=10
)
Ezvol = mp.Volume(center=mp.Vector3(0, 0, 2.5),
                  size=mp.Vector3(), dims=2, is_cylindrical=True)
Ez = mpa.FourierFields(sim, Ezvol, mp.Ez)

The error is the same regardless of if dims or is_cylindrical are passed to mp.Volume

Interestingly this error occurs in the current *conda version of meep (1.24.0), but the older Ubuntu package manager version (1.17.1) does not produce any error.

[mawc2019]

As the error appears at sim._fit_volume_to_simulation, the MWE can be further reduced as follows, which does not involve any part of the adjoint solver.

import meep as mp
import meep.adjoint as mpa
pml_layers = [mp.PML(1.0)]
sim = mp.Simulation(
    cell_size=mp.Vector3(3, 0, 3),
    boundary_layers=pml_layers,
    dimensions=mp.CYLINDRICAL,
    m=0,
    default_material=mp.Medium(index=1.0),
    resolution=10
)
Ezvol = mp.Volume(center=mp.Vector3(0, 0, 2.5),
                  size=mp.Vector3(), dims=2, is_cylindrical=True)
sim._fit_volume_to_simulation(Ezvol)

Adding the following three lines after this line can fix the bug exposed by the MWE.

        if self.dimensions == mp.CYLINDRICAL:
            self.dimensions = 2
            self.is_cylindrical = True

I could not find the reason for the volume dimension to be set to -2.

When mp.CYLINDRICAL is printed, it gives -2.

Interestingly this error occurs in the current *conda version of meep (1.24.0), but the older Ubuntu package manager version (1.17.1) does not produce any error.

The FourierFields adjoint solver was overhauled before the version 1.23.0. The function _fit_volume_to_simulation was not used in the old version of FourierFields.

[ejohlin]

Adding the following three lines after this line can fix the bug exposed by the MWE.

        if self.dimensions == mp.CYLINDRICAL:
            self.dimensions = 2
            self.is_cylindrical = True

Thank you, I can confirm that this does indeed fix the issue.