Domain wall simulation

Initialize a domain wall configuration with the --init dw option:

$ llg3d --solver opencl --n_profile 1 --precision single --init dw --T 1300 --Jy 81 --Jz 81 --N 20
Initializing OpenCL solver...
Initializing context...
---
	x		y		z
J	300		81		81
L	2.99000000e-07	8.00000000e-08	8.00000000e-08
d	1.00000000e-09	1.00000000e-09	1.00000000e-09
---
dV    = 1.00000000e-27
V     = 1.91360000e-21
ntot  = 1968300
ncell = 1913600
---
Failed to read file: /tmp/dep-acf35a.d
/builds/llg3d/llg3d/.venv/lib/python3.11/site-packages/pyopencl/__init__.py:570: CompilerWarning: Non-empty compiler output encountered. Set the environment variable PYOPENCL_COMPILER_OUTPUT=1 to see more.
  lambda: self._prg.build(options_bytes, devices),
build program: kernel 'predict' was part of a lengthy uncached source build (assuming cached by ICD) (0.20 s)
element         : Cobalt
N               = 20
dt              = 1e-14
Jx              = 300
Jy              = 81
Jz              = 81
dx              = 1e-09
T               = 1300.0
H_ext           = 0.0
init_type       : dw
result_file     : run.npz
start_averaging = 4000
n_mean          = 1
n_profile       = 1
solver          : opencl
precision       : single
blocking        = False
seed            = 12345
device          : auto
profiling       = False
verbosity       : INFO
np              = 1


  0%|          | 0/20 [00:00<?, ?it/s]Failed to read file: /tmp/dep-5fe647.d
build program: kernel 'rng_gen_philox4x32_normal' was part of a lengthy uncached source build (assuming cached by ICD) (0.26 s)

  5%|▌         | 1/20 [00:00<00:05,  3.45it/s]
 40%|████      | 8/20 [00:00<00:00, 25.37it/s]
 75%|███████▌  | 15/20 [00:00<00:00, 39.55it/s]
100%|██████████| 20/20 [00:00<00:00, 35.52it/s]N iterations          = 20
total_time [s]        = 0.585
time/ite [s/ite]      = 2.924e-02
efficiency [s/ite/pt] = 1.486e-08
CFL                   = 7.543e-02
Saving run.npz

This will create a domain wall in the yz plane at the center of the sample. The magnetization will point in the +x direction on the left side of the wall and in the -x direction on the right side of the wall.

The --n_profile 1 option specifies that the magnetization profile along the x direction will be saved every time step. Longitudinal profiles are created by averaging the magnetization in the yz plane and stored in the x_profiles key of the result file:

$ llg3d.info run.npz
...
results/records
x_profiles
    t
            shape: (21,), dtype: float64
    m1
            shape: (21, 300), dtype: float32
    m2
            shape: (21, 300), dtype: float32
    m3
            shape: (21, 300), dtype: float32
xyz_average
        shape: (21, 2), dtype: float64

Now, to vizualize the domain wall profile at different time steps (see llg3d.post.x_profiles):

$ llg3d.x_profiles run.npz -m 1 -t ::2 -i x_profiles_2.png
Written to x_profiles_2.png