Usage
Running the Code
Examples
Minimal run with all defaults:
Spectrum initial conditions and expanding cosmology:
./qaxions --N 256 --steps 1000 --nmeas 30 --meas 1 --ic spectrum --cosmo 1
Command-Line Options
Grid & Simulation
| Flag | Type | Default | Description |
--N <int> | integer | 64 | Number of grid points per dimension |
--dim <int> | integer | 3 | Spatial dimension (must be 2 or 3) |
--L <float> | float | 1.0 | Physical box size |
--dt <float> | float | 0.0001 | Time step size |
--steps <int> | integer | 10 | Number of simulation steps |
--nmeas <int> | integer | 20 | Number of steps between measurements |
Initial Conditions & Physics
| Flag | Type | Default | Description |
--ai <float> | float | 0.1 | Initial scale factor |
--alpha <float> | float | 4000 | Gravity strength |
--seed <int> | integer | 9 | Random seed |
--ic <string> | string | solitons | Initial condition type: solitons or spectrum |
--cosmo <int> | integer | 0 | Cosmology type: 0 = static, 1 = expanding |
Output & Measurements
| Flag | Type | Default | Description |
--dir <path> | string | output | Output directory |
--meas <int> | integer | 0 (NONE) | Measurement flags (bitmask, see below) |
--verb | boolean flag | false | Enable verbose output |
| Flag | Type | Default | Description |
--nthr <int> | integer | 1 | Number of OpenMP threads |
--fft <0–3> | integer | 0 | FFTW plan type |
--fft — FFTW Plan Type
| Value | Description |
0 | ESTIMATE (default, fastest to plan) |
1 | MEASURE |
2 | PATIENT |
3 | EXHAUSTIVE (slowest to plan, fastest to execute) |
Higher values spend more time finding an optimal FFT plan, which can pay off for long runs on fixed grid sizes.
Getting Help