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read_grid command


read_grid filename keyword args ... 


read_grid data.grid
read_grid data.grid custom temperature double 0 


Read a grid file in text format which lists the grid cell IDs to be used to construct a hierarchical grid that overalys the simulation domain defined by the create_box command. The grid can also be defined by the create_grid command.

The grid file can be written by the write_grid command in a previous simulation, or be created by some pre-processing tool. See Section 6.8 of the manual for a definition of hierarchical grids and grid cell IDs as used by SPARTA.

The specified file can be a text file or a gzipped text file (detected by a .gz suffix). See the write_grid command for a description of the format of the file.

The grid cell IDs read from the file (one per line) are assigned to processors in a round-robin fashion, which means in general the set of cells a processor owns will not be contiguous in a geometric sense. They are thus assumed to be a "dispersed" assignment of grid cells to each processor.

IMPORTANT NOTE: See Section 6.8 of the manual for an explanation of clumped and dispersed grid cell assignments and their relative performance trade-offs. The balance_grid command can be used after the grid is read, to assign child cells to processors in different ways. The "fix balance" command can be used to re-assign them in a load-balanced manner periodically during a running simulation.

The custom keyword allows a custom per-grid vector or array to be created and initialized. Custom vectors or arrays associate a single value or multiple values with each grid cell. They can be output by the dump grid command and uses as inputs by other commands. For example, many of the models for the surf_collide command take temperature as an input; use of a per-surf vector allows the temperature of individual surface elements to be specified.

The name argument is the name assigned to the new custom vector or array. The datatytpe argument is int or float which determines whether the vector/array stores integer or floating point values. The Nc argument is 0 for a per-surgrid vector and an integer >= 1 for an array with Nc columns. A per-grid vector stores a single value per grid cell; a per-grid array stores Nc values per grid cell.

Each use of the custom keyword determines how many values are appended for each line following the grid cell ID. For a custom per-grid vector, a single value is appended. For a custom per-grid array, Nc values are appended. The values are assigned to custom vectors or arrays in the order the custom keywords are specified. For example, for this read_grid command, 4 custom values should be added to the end of each line in the Cells section of the input file:

read_grid custom temperature float 0 custom flags int 3 

The first floating-point value will be the temperature, the next 3 integers will be flags.


This command can only be used after the simulation box is defined by the create_box command.

To read gzipped grid files, you must compile SPARTA with the -DSPARTA_GZIP option - see Section 2.2 of the manual for details.

Related commands:

create_box, create_grid, write_grid

Default: none