CarpetIOASCII

Erik Schnetter <schnetter@aei.mpg.de>
Thomas Radke <tradke@aei.mpg.de>

November 20, 2005

Abstract

This thorn reproduces thorn IOASCII from arrangement CactusBase but is specifically for the driver thorn Carpet.

1 Introduction

This thorn provides ASCII output of data in 1, 2 or 3 dimensions. It reproduces most of the functionality of thorn IOASCII from the standard CactusBase arrangement. Where possible the names of parameters and their use is identical. For most purposes it should be sufficient to take a parameter file written for the standard IOASCII and just change the active thorn.

However, this thorn outputs considerably more information than the standard IOASCII thorn. Information about, e.g., the refinement level and the index position of the output are also given. All the output can be visualized using gnuplot.

The CarpetIOASCII I/O methods can output any type of CCTK grid variables (grid scalars, grid functions, and grid arrays of arbitrary dimension); data is written into separate files named "<varname>.asc".

2 CarpetIOASCII Parameters

The most important parameters to control the CarpetIOASCII I/O methods are listed below. Many parameters come as a set of four individuals, one for each I/O method, controlling 0, 1, 2, or 3-dimensional ASCII output respectively.

3 Using the flesh I/O API to produce ASCII output

Periodic output of grid variables is usually specified via I/O parameters in the parameter file and then automatically triggered by the flesh scheduler at each iteration step after analysis. If output should also be triggered at a different time, one can do that from within an application thorn by invoking one of the CCTK_OutputVar*() I/O routines provided by the flesh I/O API (see chapter B8.2 “IO” in the Cactus Users Guide). In this case, the application thorn routine which calls CCTK_OutputVar*() must be scheduled in level mode.

If output for a variable is required also for intermediate timesteps this can be achieved by calling CCTK_OutputVarAs*() with a different alias name; output for the same variable is then written into different ASCII files based on the alias argument.

4 Utilities