Documentation/ProgrammerGuide/Output Structure

A final important data structure defined in /athena/src/athena.h is used for outputs. Each <output> block in an input file creates a new element in an array whose members are the following structure:

typedef struct Output_s{
  int n;          /* the N from the <outputN> block of this output */
  Real dt;        /* time interval between outputs  */
  Real t;         /* next time to output */
  int num;        /* dump number (0=first) */
  char *out;      /* variable (or user fun) to be output */
  char *id;       /* filename is of the form <basename>[.idump][.id].<ext> */

/* level and domain number of output (default = [-1,-1] = output all levels) */

  int nlevel, ndomain;

/* variables which describe data min/max */
  Real dmin,dmax;   /* user defined min/max for scaling data */
  Real gmin,gmax;   /* computed global min/max (over all output data) */
  int sdmin,sdmax;  /* 0 = auto scale, otherwise use dmin/dmax */

/* variables which describe coordinates of output data volume */
  int ndim;       /* 3=cube 2=slice 1=vector 0=scalar */
  int reduce_x1;  /* flag to denote reduction in x1 (0=no reduction) */
  int reduce_x2;  /* flag to denote reduction in x2 (0=no reduction) */
  int reduce_x3;  /* flag to denote reduction in x3 (0=no reduction) */
  Real x1l, x1u;  /* lower/upper x1 range for data slice  */
  Real x2l, x2u;  /* lower/upper x2 range for data slice  */
  Real x3l, x3u;  /* lower/upper x3 range for data slice  */

/* variables which describe output format */
  char *out_fmt;  /* output format = {bin, tab, hdf, hst, pgm, ppm, ...} */
  char *dat_fmt;  /* format string for tabular type output, e.g. "%10.5e" */
  char *palette;  /* name of palette for RGB conversions */
  float *rgb;     /* array of RGB[256*3] values derived from palette */
  float *der;     /* helper array of derivatives for interpolation into RGB */

/* pointers to output functions; data expressions */
  VOutFun_t out_fun; /* output function pointer */
  VResFun_t res_fun; /* restart function pointer */
  ConsFun_t expr;     /* pointer to expression that computes quant for output */


As can be seen, all of the information associated with the output (variables to be written, format, frequency of output, etc.) are stored in this structure. The functions in the file output.c should be consulted for more details.