Field Layout
-----------------

Arguments:

  * `npw` (int array) - Number of grid points (plane waves) used in each dimension. Powers of two will result in optimal performance. Length is equal to number of dimensions.
  * `npw = "auto"` (str) - Automatically set number of grid points using cell dimenstions and the minimum species smearing length. By default only included possibilities 
      that are factors of 2 and 3 but this can be manually specified by using "autoXY" where `X` is a sequence of integers. For example `auto2` will only allow factors of 2, 
      `auto235` allows factors of 2,3,5 etc. Note that this requires all species smearing lengths to be non-zero.
  * `random_seed` (int) - seed for random number generator. Random number generator is used for initializing fields at random, or for complex langevin sampling, etc. 
  * `backend` (str) - backend to use for all fieldlib based calculations. Options: `SERIAL`, `OMP` (OpenMP), `CUDA` (Nvidia GPUs) and `HIP` (AMD GPUs). If not specified, the code will choose for you. You can also tell the code what backend to choose by setting the `FIELDLIB_BACKEND` env variable.

Example (python) ::

  import openfts
  fts = openfts.OpenFTS()
  ... 
  fts.field_layout(npw=[64],random_seed=1)
  fts.field_layout(npw="auto",random_seed=1)
  fts.field_layout(npw="auto2",random_seed=1)
  ...


Example (json) ::

  "fieldlayout": {
    "npw": [ 32, 32 ],
    "random_seed": 1
  },

  "fieldlayout": {
    "npw": "auto",
    "random_seed": 1
  },