Grid Specification

• Zone Grid Coordinates
  • cg_grid_write - Create a GridCoordinates_t node
  • cg_ngrids - Get number of GridCoordinates_t nodes
  • cg_grid_read - Get name of a GridCoordinates_t node
  • cg_coord_write - Write grid coordinates
  • cg_coord_partial_write - Write subset of grid coordinates
  • cg_ncoords - Get number of coordinate arrays
  • cg_coord_info - Get info about a coordinate array
  • cg_coord_read - Read grid coordinates
• Element Connectivity
  • cg_section_write - Write element data
  • cg_section_partial_write - Write subset of element data
  • cg_parent_data_write - Write parent info for an element section
  • cg_parent_data_partial_write - Write subset of parent info for an element section
  • cg_nsections - Get number of element sections
  • cg_section_read - Get info for an element section
  • cg_section_read_ext - Get info for an element section, including parent data range
  • cg_ElementDataSize - Get size of element connectivity data array
  • cg_elements_read - Read element data
  • cg_elements_read_ext - Read subset of element data
  • cg_npe - Get number of nodes for an element type
• Axisymmetry
  • cg_axisym_write - Create axisymmetry data
  • cg_axisym_read - Read axisymmetry data
• Rotating Coordinates
  • cg_rotating_write - Create rotating coordinates data
  • cg_rotating_read - Read rotating coordinates data

Zone Grid Coordinates

GridCoordinates_t nodes are used to describe grids associated with a particular zone. The original grid must be described by a GridCoordinates_t node named GridCoordinates. Additional GridCoordinates_t nodes may be used, with user-defined names, to store grids at multiple time steps or iterations. In addition to the discussion of the GridCoordinates_t node in the SIDS and File Mapping manuals, see the discussion of the ZoneIterativeData_t and ArbitraryGridMotion_t nodes in the SIDS manual.

Functions	Modes
ier = cg_grid_write(int fn, int B, int Z, char *GridCoordName,       int *G);	- w m
ier = cg_ngrids(int fn, int B, int Z, int *ngrids);	- w m
ier = cg_grid_read(int fn, int B, int Z, int G,       char *GridCoordName);	r - m
call cg_grid_write_f(fn, B, Z, GridCoordName, G, ier)	- w m
call cg_ngrids_f(fn, B, Z, ngrids, ier)	- w m
call cg_grid_read_f(fn, B, Z, G, GridCoordName, ier)	r - m

Input/Output

	fn		CGNS file index number.
	B		Base index number, where 1 ≤ B ≤ nbases.
	Z		Zone index number, where 1 ≤ Z ≤ nzones.
	G		Grid index number, where 1 ≤ G ≤ ngrids.
	ngrids		Number of GridCoordinates_t nodes for zone Z.
	GridCoordinateName		Name of the GridCoordinates_t node. Note that the name "GridCoordinates" is reserved for the original grid and must be the first GridCoordinates_t node to be defined.
	ier		Error status.

The above functions are applicable to any GridCoordinates_t node.

Functions	Modes
ier = cg_coord_write(int fn, int B, int Z, DataType_t datatype,       char *coordname, void *coord_array, int *C);	- w m
ier = cg_coord_partial_write(int fn, int B, int Z,       DataType_t datatype, char *coordname, int *range_min,       int *range_max, void *coord_array, int *C);	- w m
ier = cg_ncoords(int fn, int B, int Z, int *ncoords);	r - m
ier = cg_coord_info(int fn, int B, int Z, int C,       DataType_t *datatype, char *coordname);	r - m
ier = cg_coord_read(int fn, int B, int Z, char *coordname,       DataType_t datatype, int *range_min, int *range_max,       void *coord_array);	r - m
call cg_coord_write_f(fn, B, Z, datatype, coordname, coord_array,      C, ier)	- w m
call cg_coord_partial_write_f(fn, B, Z, datatype, coordname,      range_min, range_max, coord_array, C, ier)	- w m
call cg_ncoords_f(fn, B, Z, ncoords, ier)	r - m
call cg_coord_info_f(fn, B, Z, C, datatype, coordname, ier)	r - m
call cg_coord_read_f(fn, B, Z, coordname, datatype,      range_min, range_max, coord_array, ier)	r - m

Input/Output

	fn		CGNS file index number.
	B		Base index number, where 1 ≤ B ≤ nbases.
	Z		Zone index number, where 1 ≤ Z ≤ nzones.
	C		Coordinate array index number, where 1 ≤ C ≤ ncoords.
	ncoords		Number of coordinate arrays for zone Z.
	datatype		Data type in which the coordinate array is written. Admissible data types for a coordinate array are RealSingle and RealDouble.
	coordname		Name of the coordinate array. It is strongly advised to use the SIDS nomenclature conventions when naming the coordinate arrays to insure file compatibility.
	range_min		Lower range index (eg., imin, jmin, kmin).
	range_max		Upper range index (eg., imax, jmax, kmax).
	coord_array		Array of coordinate values for the range prescribed.
	ier		Error status.

The above functions are applicable only to the GridCoordinates_t node named GridCoordinates, used for the original grid in a zone. Coordinates for additional GridCoordinates_t nodes in a zone must be read and written using the cg_array_xxx functions.

When writing, the function cg_coord_write will automatically write the full range of coordinates (i.e., the entire coord_array). The function cg_coord_partial_write may be used to write only a subset of coord_array.

If the file was opened in "write mode", using cg_coord_partial_write will overwrite existing coordinates only for the specified range. In "modify mode", the existing coordinates will first be deleted, then replaced by the new coordinates.

The function cg_coord_read returns the coordinate array coord_array, for the range prescribed by range_min and range_max. The array is returned to the application in the data type requested in datatype. This data type does not need to be the same as the one in which the coordinates are stored in the file. A coordinate array stored as double precision in the CGNS file can be returned to the application as single precision, or vice versa.

In Fortran, when using cg_coord_read_f to read 2D or 3D coordinates, the extent of each dimension of coord_array must be consistent with the requested range. When reading a 1D solution, the declared size can be larger than the requested range. For example, for a 2D zone with 100 × 50 vertices, if range_min and range_max are set to (11,11) and (20,20) to read a subset of the coordinates, then coord_array must be dimensioned (10,10). If coord_array is declared larger (e.g., (100,50)) the indices for the returned coordinates will be wrong.

Element Connectivity

If the specified Elements_t node doesn't yet exist, it may be created using either cg_section_write or cg_section_partial_write. If the Elements_t node does exist (created by using either cg_section_write or cg_section_partial_write), calls to cg_section_partial_write will replace the existing connectivity data with the union of the existing and new data, with the new data overwriting the old data for common indices. The resulting index range for the new data must be continuous.

The function cg_parent_data_write will automatically write the full range of parent data (i.e., the entire ParentData array). If parent data does not exist for the specified Elements_t node, the first use of cg_parent_data_partial_write will add it. If parent data does exist (created by using either cg_parent_data_write or cg_parent_data_partial_write), calls to cg_parent_data_partial_write will replace the existing parent data with the union of the existing and new data, with the new data overwriting the old data for common indices. The resulting index range for the new data must be continuous.

The "partial write" capability described above requires that the file be opened in "write mode". For both cg_section_partial_write and cg_parent_data_partial_write, if the file was opened in "modify mode", the existing connectivity or parent data will first be deleted, then replaced by the new data.

The function cg_section_read_ext returns the same information as cg_section_read, plus the index range for the parent data.

The function cg_elements_read returns all of the element connectivity and parent data. Specified subsets of the element connectivity and parent data may be read using cg_elements_read_ext.

Axisymmetry

This node can only be used for a bi-dimensional model, i.e., PhysicalDimension must equal two.

Rotating Coordinates