Change Soft convergence criterion
Altair EmployeeHello,
when i start an optimization with optistruct the calculation is finished after 1 Iteration. In the Output-file i found following Information:
Soft convergence criterion satisfied;
the design did not change during the last Iteration.
What does this mean?
I already did a lot of successful shape-optimizations but in this case i don't really know why the shape didn't change.
I changed the default OBJTOL value from the opti control card but the problem still occurs.
The most interesting thing is:
When i change the inital value in the shape panel to 0.5 I don't have any problems and the optimization finds the best shape. When I start with an inital value of 0.0 then i get the problem with the soft convergence criterion.
Thank you
Greets,
Fatih Uysal
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Altair Employee Thank you Rahul for the Information.
Since Optistruct is a gradient based optimizer i guess optistruct stopped optimization after finding a local optimum.
Using a DGLOBAL-Card helped me to find the global optimum.
Greets,
Fatih Uysal
Thanks for the update.
Soft convergence is achieved when there is little or no change in the design variables for two consecutive iterations. It is not necessary to evaluate the objective (or constraints) for the final design point, as the model is unchanged from the previous iteration. Therefore, soft convergence requires one less iteration than regular.
Attached document should help you in understanding the process in detail
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