I/O Methods in Cactus

Cactus has several I/O methods for the output of grid variables in different data formats and styles. Each I/O method comes with its own parameters by which it can be customised, and all methods are registered with the flesh, satisfying the Cactus API, allowing them to be called directly from application thorns. An I/O method registers itself with the flesh along with it's name, and these registered names are the labels we now use to describe the various methods.

Table A6.1: Standard I/O methods provided with the Cactus distribution

I/O method	Description	Providing Thorn
Scalar	output of scalars or grid array reductions in xgraph or gnuplot format	CactusBase/IOBasic
Info	screen output of scalars or grid array reductions	CactusBase/IOBasic
IOASCII_1D	1D line output of grid arrays in xgraph or gnuplot format	CactusBase/IOASCII
IOASCII_2D	2D slice output of grid arrays in gnuplot format	CactusBase/IOASCII
IOASCII_3D	full output of 3D grid arrays in gnuplot format	CactusBase/IOASCII
IOJpeg	2D slice output of grid arrays in jpeg image format	CactusIO/IOJpeg
IOHDF5	full output of arbitrary grid variables in HDF5 format	CactusPUGHIO/IOHDF5
IOFlexIO_2D	2D slice output of grid arrays in FlexIO format	CactusPUGHIO/IOFlexIO
IOFlexIO	full output of arbitrary grid variables in FlexIO format	CactusPUGHIO/IOFlexIO

The standard provided Cactus I/O methods are shown in Table A6.1. As described above, each of these I/O thorns inherit parameters from thorn IOUtil, which must be included in your ThornList and activated in your parameter files before any of these I/O methods can be used. IOUtil allows you to set the default behaviour for all the I/O methods described above, for example, setting the parameter IO::out_every = 1 will result in any chosen I/O method providing output on each iteration. The default behaviour can be overridden by specific parameters for each method. For example, you may want scalar and 1D output at every iteration but computationally expensive 3D output only every 10th iteration, with these files going into another directory on a scratch partition.