Physical Data

• Data Arrays
  • cg_array_write - Write data array
  • cg_array_general_write - Write shaped array to a subset of data array
  • cg_narrays - Get number of data arrays under current node
  • cg_array_info - Get data array info
  • cg_array_read - Read data array
  • cg_array_read_as - Read data array as a certain type
  • cg_array_general_read - Read subset of data array to a shaped array
• Data Class
  • cg_dataclass_write - Write data class
  • cg_dataclass_read - Read data class
• Data Conversion Factors
  • cg_conversion_write - Write conversion factors
  • cg_conversion_info - Get conversion factors data type
  • cg_conversion_read - Read conversion factors
• Dimensional Units
  • cg_units_write - Write first five dimensional units
  • cg_unitsfull_write - Write all eight dimensional units
  • cg_nunits - Get number of dimensional units
  • cg_units_read - Read first five dimensional units
  • cg_unitsfull_read - Read all eight dimensional units
• Dimensional Exponents
  • cg_exponents_write - Write first five dimensional exponents
  • cg_expfull_write - Write all eight dimensional exponents
  • cg_nexponents - Get number of dimensional exponents
  • cg_exponents_info - Get exponent data type
  • cg_exponents_read - Read first five dimensional exponents
  • cg_expfull_read - Read all eight dimensional exponents

Data Arrays

The function cg_array_general_write may be used to write from a subset of the array in memory to a subset of the array in the file. When using the partial write, any existing data from range_min to range_max will be overwritten by the new values. All other values will not be affected.

The functions cg_array_general_read and cg_array_general_write allow for type conversion when both reading from and writing to the file.

When using cg_array_general_write and cg_array_general_read, the lower core elements in the file have index 1 for defining range_min and range_max; whereas for the array in memory, defined by mem_rank and mem_dimensions, the lower array elements in memory have index 1 for defining mem_range_min and mem_range_max. The actual lower and upper bounds of the array in memory can be anything. For example, to fully read a two-dimensional 6 × 6 data array with 1 rind plane on each side in the file to an 8 × 8 array in memory (mem_rank = 2 and mem_dimensions = (8,8)), set range_min and range_max to (0,0) and (7,7), and set mem_range_min and mem_range_max to (1,1) and (8,8).

Data Class

The data classes currently supported in CGNS are:

	Dimensional		Regular dimensional data.
	NormalizedByDimensional		Nondimensional data that is normalized by dimensional reference quantities.
	NormalizedByUnknownDimensional		All fields and reference data are nondimensional.
	NondimensionalParameter		Nondimensional parameters such as Mach number and lift coefficient.
	DimensionlessConstant		Constant such as π.

These classes are declared within typedef DataClass_t in cgnslib.h, and as parameters in cgnslib_f.h.

Data Conversion Factors

The DataConversion_t data structure contains factors to convert the nondimensional data to "raw" dimensional data. The scaling and offset factors are contained in the two-element array ConversionFactors. In pseudo-Fortran, the conversion process is as follows:

   ConversionScale  = ConversionFactors(1)
   ConversionOffset = ConversionFactors(2)
   Data(raw) = Data(nondimensional)*ConversionScale + ConversionOffset

Dimensional Units

The supported units are declared within typedefs in cgnslib.h and as parameters in cgnslib_f.h.

When reading units data, either cg_units_read or cg_unitsfull_read may be used, regardless of the number of units used in the file. If cg_unitsfull_read is used, but only five units are used in the file, the returned values of current, amount, and intensity will be CG_Null.

Dimensional Exponents

When reading exponent data, either cg_exponents_read or cg_expfull_read may be used, regardless of the number of exponents used in the file. If cg_exponents_read is used, but all eight exponents are used in the file, only the first five exponents are returned. If cg_expfull_read is used, but only five exponents are used in the file, the returned values of the exponents for electric current, substance amount, and luminous intensity will be zero.