5.3.10 Process Time Management

In this group several parameters can be set which control the start of the time counting during a simulation and the total length of a job. If either one of the halt conditions below is met, COBOLD finishes the current step, writes a final model (plus some final information to other files), and stops execution.

For example on a CRAY one typically wants to use most of the CPU time given for an individual batch job. In this case one can set e.g. real cputime_remainlimit=2000.0 and the values for the other halt conditions to -1.0 or -1.

• real starttime:
  The start time of a simulation is usually taken from the start model file. But sometimes is simulation is to be started with the final model of a previous run but should start at time=0.0. This can be achieved by setting the start time with

  real starttime f=E15.8 b=4 n='Start time'                              u=s
  0.0
  

  Allowed values are
  • $\geq$ 0.0: Set the initial time of the simulation to this value and override value from start model.
  • $<$ 0.0: (default) Take the initial time from start model.

• integer starttimestep:
  The start time step count of a simulation is usually taken from the start model file. But sometimes is simulation is to be started with the final model of a previous run but should start at time step=0. This can be achieved by setting the start time step count with

  integer starttimestep f=I11 b=4 n='Start time step number'             u=1
  0
  

  Allowed values are
  • $\geq$ 0: Set the initial time step of the simulation to this value and override value from start model.
  • $<$ 0: (default) Take the initial time step count from start model.

• real cputime:
  Because of the long simulation time usually COBOLD will run in some sort of batch mode which might impose limits on the execution time per run. On a CRAY the CPU time that is left can be accessed with a special subroutine (in call tremain in rhd_mac_cray_module.f90). On other machines it is possible to specify the allowed total time for the job e.g. with

  real cputime f=E15.8 b=4 n='CPU time'                                  u=s
  1000000.0
  

  During the run of COBOLD the leftover CPU time is computed by subtracting the used CPU time (which is given by e_time=etime(tarray) in rhd_mac_sun_module.f90) from the specified total CPU time for the job.

• real cputime_remainlimit:
  Because COBOLD needs some time to finish the last time step it should start exiting well before all CPU time is used up. This amount of buffer CPU time can be specified e.g. with

  real cputime_remainlimit f=E15.8 b=4 n='maximum remaining CPU time'    u=s
  2000.0
  

  Its value depends on the size of the model and the speed of the machine (more precisely the maximum CPU time per time step).

• real endtime:
  If the simulation should run up to a certain (stellar) time, its values can be specified e.g. with

  real endtime f=E15.8 b=4 n='total simulation time limit'               u=s
  10000.0
  

  A value $<$ 0.0 deactivates this halt condition: it is not checked at all. If this parameter is set to a non-negative value a follow-up simulation should not use the same parameter file: it would stop immediately.

• real plustime:
  If the initial model should be advanced by a certain (stellar) time span, this value can be set e.g. with

  real plustime f=E15.8 b=4 n='simulation advance time'                  u=s
  5.0E+07
  

  A value $<$ 0.0 cancels this halt condition: it is not checked at all. This condition assures (if it is the only one) that all individual simulation runs cover (approximately) the same stellar time.

• integer endtimestep:
  If the simulation should run up to a certain time step, its values can be specified e.g. with

  integer endtimestep f=I11 b=4 n='total simulation time step number'    u=1
  1234
  

  This might be useful to advance the simulation up to a point shortly before a previous simulation crashed. A value $<$ 0 cancels this halt condition: it is not checked at all.

• integer plustimestep:
  If the initial model should be advanced by a certain number of time steps their number can be set e.g. with

  integer plustimestep f=I11 b=4 n='simulation advance time step number' u=1
  2000
  

  A value $<$ 0 deactivates this halt condition: it is not checked at all.