Default Convergence CriteriaFor sensitivity-based optimization, the optimization stops automatically when the following convergence criteria are fulfilled. More detailed explanations of the criteria can be found in the sections beneath.
Automatic Creation of Stop Conditions
For sensitivity-based optimization, some convergence stop criteria that
consider the change of the objective function and the change in the design
variables can be created. The creation of the convergence criteria can be
influenced with the
Stop Criterion: Change in Objective FunctionOne of the available stop criteria is a measurement based on the change in the objective function from one optimization design cycle to the next design cycle. This stop criterion is defined by
where Θ is objective value, the index n is representing the present optimization iteration and is n-1 is the
previous iteration. When the criterion is lower than
This could be desirable when the number of optimizations should be reduced. Stop Criterion: Change in design variablesAnother stop criterion is based on the change in the design variables from one optimization design cycle to the next optimization design cycle and is defined by:
where the index n is representing the present optimization iteration and is n-1 is the
previous iteration. When the criterion is lower than
Convergence CriteriaBy default, the stop criterion measuring the change in the objective function
and the criterion measuring the change in the design variables should both be fulfilled before the optimization
algorithm stops. To specify that just one of the criteria must be
fulfilled, set In the example below, the optimization algorithm should stop when just one of the criteria is fulfilled
Enhanced Convergence CriteriaFor shape optimization, typical stop conditions can be defined more directly by an enhanced stop command:
For details about the parameters, see STOP. Using this enhanced stop command, the extraction of variables and their logical comparison is performed internally by SIMULIA Tosca Structure and need no longer be specified manually by the user. For a detailed description of the several items, refer to the commands manual. Start Iteration for Convergence CheckThe two convergence criteria above are not checked before a specified number of optimization
iterations have been executed. This means that the optimization will always be executed
until
The default value for
Example 1:The stop condition is fulfilled, if the maximum equivalence stress
in the node group
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