Clocks for Timing

To add a Cactus clock, you need to write several functions to provide the timer functionality (see Section B10.1), and then register these functions with the flesh as a named clock.

The function pointers are placed in function pointer fields of a cClockFuncs structure. The fields of this structure are are:

create

void *(*create)(int)

destroy

void (*destroy)(int, void *)

start

void (*start)(int, void *)

stop

void (*stop)(int, void *)

reset

void (*reset)(int, void *)

>et

void (*get)(int, void *, cTimerVal *)

set

void (*set)(int, void *, cTimerVal *)

n_vals

int

The first int argument of the functions may be used in any way you see fit.

The n_vals field holds the number of elements in the vals array field of the cTimerVal structure used by your timer (usually 1).

The return value of the create function will be a pointer to a new structure representing your clock.

The second void* argument of all the other functions will be the pointer returned from the create function.

The get and set functions should write to and read from (respectively) a structure pointed to by the cTimerVal* argument:

typedef enum {val_none, val_int, val_long, val_double} cTimerValType;

typedef struct
{
  cTimerValType type;
  const char *heading;
  const char *units;
  union
 {
    int        i;
    long int   l;
    double     d;
  } val;
  double seconds;
  double resolution;
} cTimerVal;

The heading field is the name of the clock, the units field holds a string describing the type held in the val field, and the seconds field is the time elapsed in seconds. The resolution field is the smallest non-zero difference in values of two calls to the timer, in seconds. For example, it could reflect that the clock saves the time value internally as an integer value representing milliseconds.

To name and register the clock with the flesh, call the function

 CCTK_ClockRegister( "my_clock_name", &clock_func ).

Appendices 45#45 3#3

Note that these appendices appear (identically) in both the Cactus Users' Guide and the Cactus Reference Manual.