Code usage

Configuration files

Simulation parameters are controlled by JSON configuration files.

Basic usage

The files have an .ini suffix and a simple structure of parameter: value. When fed into the drivers, Runko will automatically parse the file and construct a Configuration object, typically called conf. Any parameter in the configuration file gets turned into conf.parameter with a value of value; this makes it easy to add any new user-defined parameters to the driver scripts.

During the construction of conf the configuratoin file is also typically passed through a problem-spesific init_problem.py file that introduces a specialiced Configuration_Problem derived from the base class. It can do additional manipulation on the configuration file parameters before resulting in a conf object.

Typical parameters

Typical default parameters found in configuration files include:

[io]: basics
- outdir: simulation output directory name (e.g., run_1)
- laprestart: Simulation lap to restart from (-1 = no restart, 0 = automatic, X lap to restart; 0 is default)
- restart: No. of steps between restart files written; these restart files are cycled and overwritten during the simulation to save disk space.
[io]: analysis
- interval: No. of steps between analysis output files written
- stride: thinning factor for analysis grids; results in saving only every st:th grid point in each dimension (typically either 1 for complete data snapshots or tile length for maximum compression)
- stride: thinning factor for analysis grids; results in saving only every st:th grid point in each dimension (typically either 1 for complete data snapshots or tile length for maximum compression)
[io]: deep io
- full_interval: No. of steps between writing of full output files (these act as full restart files but are not overwritten; typically -1 to save disk space)
[io]: shock io (optional and relevant only for shock simulations)
- box_nx: length of a special grid that tracks the shock front during a simulation
- box_stride: similar thinning factor as stride but for the special shock grid
- box_shift: displacement of the box from the (automatically-located) shock front (use a value of -box_nx/2 to center the grid on the shock front; 0 to track upstream).
[simulation]: MPI control parameters (optional)
- mpi_track: instead of partitioning the domain equally between processors we can optionally make a “caterpillar`-like track (along x-dimension) where tiles owned by different MPI ranks repeat themselves cyclically. This parameter controls the length of the track in units of tiles. A value of 128 would partition the tiles inside a sub-domain of 128 x Ny x Nz equally between all the processors. The pattern is repeated for the length of the domain in x-direction.
  
  make sure there are reasonable number of tiles in one cycle per processor. Each rank has mpi_track x Ny x Nz/Nprocs continuous tiles in the subdomain, multiplied by the number of cycles, Nx/mpi_track. - The parameter can be tuned to roughly equal the active zone in a shock simulation. This way the simulation is always distributed among approximiately the same number of ranks. Physical length of the track is mpi_track * NxMesh/c_omp.