Schedule Options

The options define various characteristics of the schedule item.

AS

This assigns a new name to a function for scheduling purposes. This is used, for instance, to allow a thorn to schedule something before or after a routine from another implementation; two thorns providing this implementation can schedule a routine AS the same thing, thus allowing other thorns to operate independently of which one is active.

WHILE

This specifies a CCTK_INT grid scalar which is used to control the execution of this item. As long as the grid scalar has a nonzero value, the schedule item will be executed repeatedly. This allows dynamic behaviour with scheduling.

IF

This specifies a CCTK_INT grid scalar which is used to control the execution of this item. If the grid scalar has a nonzero value, the schedule item will be executed, otherwise the item will be ignored. This allows dynamic behaviour with scheduling.

If both an IF and a WHILE clause are present, then the schedule is executed according to the following pseudocode:

IF condition
  WHILE condition
    SCHEDULE item
  END WHILE
END IF

BEFORE or AFTER

These specify either

• a function or group before or after which this item will be scheduled, or
• a list of functions and/or groups; this item will be scheduled (once) before any of them or after all of them respectively.

Note that a single schedule item may have multiple BEFORE and/or AFTER options; the scheduler will honor all of these (or abort with a fatal error). For example,

schedule FOO BEFORE A BEFORE B BEFORE C ...

schedules FOO before any of A, B, or C. This can also be written

schedule FOO BEFORE (A B C) ...

Note that the set of all BEFORE/AFTER options in all active schedule blocks of all active thorns, must specify a (directed) graph with no cycles; if there are any cycles, then the scheduler will abort with a fatal error.