global.data Explained

Arguably the most important data file in AstroBEAR 2.0, global.data contains global domain and solver data. This data is broken up into several namelists, which are read in by different sections of the code.

GlobalData

The GlobalData namelist contains global parameters. These parameters hold for the entire problem domain, and many of them actually describe it.

• nDim: The number of dimensions in the problem. For AstroBEAR, this should be either 2 or 3, since AstroBEAR only does 2D and 3D problems. A 1D problem can be approximated with a long, narrow 2D problem domain.

• MaxLevel: The maximum refinement level for this simulation. MaxLevel is the number of refinement levels over the base grid (so a MaxLevel of 0 is fixed-grid). This value can never be less than 0, and if it is greater than 0 then the problem is an AMR problem.

• MinimumGridPoints: The minimum number of cells per dimension that a grid can have. Since a grid must have at least one cell, MinimumGridPoints should never be less than 1. A low MinimumGridPoints allows AstroBEAR to create smaller grids, which lets it refine more efficiently. Low MinimumGridPoints values also run the risk of creating a lot more grids, which will boost administrative and communication costs.

• nDomains: The number of domains comprising the problem domain. Multiple domains are useful if you want to impose different physical processes in different regions of your problem domain (i.e., different cooling curves), but most problems do not require this degree of complexity. Unless you have a specific reason for wanting multiple domains in your problem, it is best to leave this set to 1.

• lRestart: Should be set to T if you intend to restart a simulation from a Chombo file, or F if you intend to start the simulation from the beginning. You must have a Chombo file in your problem's out/ directory if you want to use this option, and it's index must match that of the RestartFrame variable (see below).

• RestartFrame: The index of the frame from which you wish to restart. This number should be greater than or equal to 0. In order to use this, you must have a Chombo file of the same index value in your problem's out/ directory (for example, RestartFrame 5 will crash unless the file out/chombo00005.hdf is present). Regardless of its value, the RestartFrame variable does nothing if the lRestart flag is set to F.

• start_time: The start time in computational units. This quantity is used to calculate the time per frame within a simulation, and should not be changed even if you are restarting the job.

• final_time: The final time (end time) in computational units. Needless to say, this should be greater than start_time.

• GmX: This is a three-integer array, with each element representing the number of cells in the domain along the given dimension. Thus, the total domain size in cells is GmX(1) * GmX(2) * GmX(3). This array is subject to the following constraints:
  • All elements must be integers.
  • All elements must be greater than or equal to MinimumGridPoints.
  • If nDim = 2, then the third GmX entry must be 1.

• GxBounds: This is a double-precision array with six values. The first three values set the lower spatial bounds of the problem domain, and the last three values set the upper bounds. For instance, the problem domain's boundaries along the x-axis are set by the first and fourth elements in GxBounds. The GxBounds array has three constraints:
  • GxBounds(1) < GxBounds(4) (i.e., they must define a legitimate x interval).
  • GxBounds(2) < GxBounds(5) (i.e., they must define a legitimate y interval).
  • IF nDim = 3, then GxBounds(3) < GxBounds(6). Otherwise, GxBounds(3) and GxBounds(6) must equal zero.
• Gmthbc: A six-integer array defining the boundary conditions along the edges of all three dimensions. If nDim = 2, then Gmthbc(3) and Gmthbc(6) should both be set to 1. The other boundary conditions can be chosen from one of the following options:
  • 1 — Extrapolated boundaries.
  • 2 — Periodic boundaries.
  • 3 — Reflecting boundaries.

LevelData

IOData

DomainData

PoissonData