tem_timeControl_module Module

This module provides functions to control explicit time stepping solvers.

It makes use of the tem_time_module with its definition of time in terms of various measurements, allowing the control of events based on these units. A time control is always active within a certain range, given by its min and max value, and emits actions to take based on the given interval. If multiple measurements are given for any of the measures, this time is always taken by that unit which occurs first. All three settings (min, max and interval) might use different time measures independently.

The time_control table takes the following form:

     time_control = {
       min = {},
       max = {},
       interval = {},
       check_iter = 123,
       delay_check = false
     }

Here min, max and interval are each time definitions, see tem_time_module. The time definition is providing, a measure of time in terms of simulation time, number of iterations and passed running time (clock): {sim = 1.0, iter = 1, clock = 60.0}.

max describes the end of the time span. If this time_control is for the overall simulation it defines the end of the run, after any of the time measures is reached, the simulation will stop.

min describes the beginning of the timespan for this control object. This may for example be used to start writing tracking data only after a certain point in time. Again, if multiple time definitions (sim, iter, clock) are defined, whichever first will be encountered will start the timespan of this control.

interval describes intervals within in the min and max points in time where something is to happen, for example that a restart file is to be written.

If a time definition is not provided as a table the given value is interpreted as specifying a time in terms of simulated time (sim). See tem_time_module for details on the time definition.

check_iter allows you to control, how often the trigger status of the time control is to be checked in terms of iterations. These checks involve communication and may have a performance impact if performed in every iteration and the iterations are very short. By setting the check_iter to some larger value the communications can be decreased as they will only be performed every check_iter iteration. Be aware that increasing the check_iter setting also decreases the accuracy for the time control. There might be performed multiple iterations beyond the intended specified trigger in this case. Typically it is not necessary to specify the check_iter setting. Without providing it a default of one will be used.

delay_check provides the option to delay the evaluation for the clock time trigger by one check interval by using a nonblocking allreduce. It relaxes the synchronization requirements, but introduces a delay in the actual triggering of the clock event. The default of this setting depends on the corresponding delay_check setting in simControl. Thus, if it is set in the simControl table itself, that setting will also be used here unless overwritten by explicitly providing it here.