Errors During Optimization

This chapter describes the errors that can occur during the optimization.

General

During the optimization, different modules (the optimization preprocessor, FE solver, the optimization module) generate the control files (log files). The control program checks the existence and contents of these control files and consequently determines if the optimization has to be continued or stopped.

DB_ERROR Directory

When the program cancels an optimization, a directory named DB_ERROR is created in the jobname directory in order to facilitate the error search. This directory contains all files that are necessary to find the error. These include the protocol file TOSCA_OUT of the optimization and the protocol files of the FE solver. In addition, the initial model, parameter file and all files and macros are present in this directory.

Log Files

The most important files used to search for error messages are the log files (see Optimization Preprocessing (TOSCA_PREP)):

  • TOSCA_OUT of the optimization: All errors that occur in TOSCA_PREP or TOSCA_OPT are documented in this file; search it for entries containing the words CRITICAL, ERROR or WARNING.
  • authorization.log (see also Special Logfiles) of the authorization process (located in the start directory of the optimization): configuration and licensing information is written to this file.
  • Solver-specific protocol files (moved to DB_ERROR directory) created by the solver. The file names depend on the used solver. For more information, please refer to the FE-solver documentation.

Result Control File

When the result file created by the solver does not contain any useful results, the optimization module generates an empty file. The control program checks the existence of this file and stops the optimization if the file is found.

Some solver results sometimes do not allow the optimization to proceed due to following reasons: a result request in the input file is incorrect (e.g., no node stresses were written in the result file); the solver cannot perform the finite element analysis due to numerical problems; element twisting, rigid body displacements due to missing boundary conditions or too large displacements occur.

A check of the previous optimization iteration and the modification of the model can be used to find the reason for a termination that affects the optimization (e.g. element twisting or too large displacements).

Screen Information

When SIMULIA Tosca Structure is started, the output that is being made during the optimization process appears on the screen and in the window of Tosca ANSA® environment or Tosca Structure.gui. The amount of information in the log file TOSCA_OUT and on screen can be controlled by requesting a certain loglevel. For more information, please see Logging.