Restart of Optimization

It is possible to restart an OptiStruct optimization by using the command line option -restart (Run Options), by adding the I/O Options Entry RESTART to the input file, or from the OptiStruct panel in HyperMesh.

To restart an optimization, you will need information about the final iteration of the previous optimization run. This information is stored in the .sh file.

The DESMAX entry on the DOPTPRM Bulk Data Entry , in the .fem file, specifies the maximum number of additional iterations. To perform an analysis on the optimized structure, restart with DESMAX set to 0. If DESMAX is not defined, the default value of DESMAX is assumed (30 iterations is the default value for DESMAX unless topology manufacturing constraints are used, in which case the default is 80 iterations).

There are a number of conditions that must be observed when restarting an optimization:
  • The number of design variables or design elements cannot be changed.
  • It is invalid to restart with minimum member size control removed, if it was present in the original run.
  • It is invalid to restart with checkerboard control turned on, if it was not activated in the original run. It is, however, acceptable to deactivate checkerboard control in the restart, if it was activated in the original run.
  • It is invalid to restart with manufacturing constraints that differ from those of the original run.

The purpose of the restart functionality is for restarting with unconverged optimization runs or optimization runs that were terminated before completion (due to a power outage, etc.).

Output files from a restart run are appended with the extension _rst#, where # is a 3 digit number indicating the starting iteration for the restart run. For example, filename_rst030.out is the .out file created when restarting filename.fem from iteration 30.

Iterations for the restart are numbered starting with the iteration number in the .sh file (the last iteration from the previous run).

You may manually append new .dens, .disp, and .strs files to old ones and post-process the combined files.