Restart Modes

An optimization is an iterative process that can run several hours or days depending on the size of the model. Different problems can arise during this process that can lead to a termination of the optimization task. SIMULIA Tosca Structure has an in-built restart possibility that can be used in order to avoid starting the complete optimization task again after a stop due to external factors. Optimization starts at the iteration where the interruption occurred.

Note:

Please note, that restart of an interrupted optimization should not be confounded with starting the (sensitivity based topology) optimization newly with an already existing material distributation. In general this initial material distribution is derived from a previous optimization run and defined using the parameter INITIAL_DV_FIELD in the command DV_TOPO.

Requirements for a restart

It is not always possible to resume the optimization after an interruption. Certain requirements have to be fulfilled to be able to restart a SIMULIA Tosca Structure optimization. A restart of an externally interrupted SIMULIA Tosca Structure job can be carried out when the following problems occur:

  • Stop of the FE analysis due to a licensing problem;
  • Stop of the FE analysis due to insufficient hard disk space;
  • Stop of the optimization module due to a lack of licenses;
  • User stop of the task (e.g. by pressing Ctrl-C in command line).
Important:

When a task interruption occurs due to problems with the optimization task formulation or due to convergence problems, a restart will not help. For example, when the finite element analysis stops because of distorted elements during shape optimization, the same problem will occur when a restart is executed.

Restart process

During a restart, all settings of the original task are used to resume the optimization. There is no possibility of modifying the settings for a restart because the parameter file cannot be loaded again. But you may change the -- logevel-parameters in the command line. The start directory of the optimization task can be moved to any location.

Important:

It is important that the relative location of the files in the job directory remains unchanged.

For example, if the task was interrupted due to insufficient hard disk space and there is no possibility to create more space on the hard disk, the complete job directory can be transferred to another hard disk and a restart can be made from there. After optimization has been stopped, the files that were created during the optimization can be found either in the directory jobname/DB_ERROR or (when the control job has been interrupted) in the working directory (jobname).

At the beginning of a restart, all data is copied into the working directory (jobname). Various methods are available for a restart:

Mode Comment
-restart (recommended) This is the standard restart mode. Program call: 
tosca <jobname> -restart
The standard restart is always started with a finite element analysis. This means, after the required data has been copied, the finite element analysis is started using the analysis model that was modified last and the optimization task is then carried out.
-restart2 (not recommended) This restart is used when the finite element analysis sequence has been completed without any errors but an interruption occurred in the optimization module. The computing time needed for the FE analysis can be saved in this case and the last result file is used by Tosca Structure for the optimization. Program call: 
tosca <jobname> -restart2
-restart3 (not recommended) This restart is used when an optimization with an integrated durability analysis is carried out. If all results of the durability analysis are available, the revised damage calculation is skipped. Program call: 
tosca <jobname> -restart3