DESVAR Versus DCONSTR - Nastran 1

[nvhuser]

Hello guys, generally in an optimization problem what would increase more the simulation time, increase the number of design variables (DESVAR) or increase the number of constraints (DCONSTR)?
Looking forward your feedback. Thanks

 

[Tuw]

Hello nvhuser,

I think increasing the number of design variable is the answer, while on the other hand, increasing the number of constraints limits the flexibility of the optimization process, thus the process is shorten...

Tuw

 

[nvhuser]

Hi Tuw, thank you for your reply.
I agree with you, I am little bit concerned about increase the number of DCONSTR from 2 to 20, but probably there is no big difference in computational time.

 

[JBlack68]

Having a lot of constraints does limit the optimization process but may not necessarily shorten it as Nastran may loop for a while to "meet" all the constraints. Some might not be feasible. I think there is an option to limit the number of loops but can't remember the parameter. Usually one tries not to have "hard" constraints such 10<maxstress<11

 

[nvhuser]

Right JXB0809, I will avoid these practices