Discrete Adjoint giving garbage values

Manish Kumar Mishra · March 3, 2018, 07:25

I was previously using continuous adjoint solver for gradient computation. I decided to try Discrete Adjoint once but I am facing a problem here.

My direct simulation works, so I have a flow solution for the adjoint solver to use. I am also able to use the Continuous Adjoint solver to compute the gradient but when I tried running the Discrete Adjoint solver, it runs and residual values drop by 10 orders but the solution is way far off and when I check the adjoint variable contour, it seems terrible. With discrete Adj solver, the solution blows up!

I thought the problem was with my problem but I am facing the same problem with the config file and grid in QuickStart tutorial airfoil problem. Continuous adj works but not discrete adj.

I tried changing a few setting but I think those shouldn't make any difference. Has anyone faced this problem? Or if you can guess it and suggest a few things to try, I will be glad.

Thank you

Sprotte · March 7, 2018, 15:35

Assuming that your SU2_CFD_AD is fine and that you are reading in the solution file correctly - does changing the objective function change the behaviour?

Sounds a bit like a problem in that direction...

March 3, 2018, 07:25	Discrete Adjoint giving garbage values	#1
Manish Kumar Mishra New Member Manish Kumar Mishra Join Date: May 2015 Posts: 1 Rep Power: 0	I was previously using continuous adjoint solver for gradient computation. I decided to try Discrete Adjoint once but I am facing a problem here. My direct simulation works, so I have a flow solution for the adjoint solver to use. I am also able to use the Continuous Adjoint solver to compute the gradient but when I tried running the Discrete Adjoint solver, it runs and residual values drop by 10 orders but the solution is way far off and when I check the adjoint variable contour, it seems terrible. With discrete Adj solver, the solution blows up! I thought the problem was with my problem but I am facing the same problem with the config file and grid in QuickStart tutorial airfoil problem. Continuous adj works but not discrete adj. I tried changing a few setting but I think those shouldn't make any difference. Has anyone faced this problem? Or if you can guess it and suggest a few things to try, I will be glad. Thank you

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March 7, 2018, 15:35		#2
Sprotte Member Ole Burghardt Join Date: Mar 2016 Location: Kiel, Germany Posts: 60 Rep Power: 10	Assuming that your SU2_CFD_AD is fine and that you are reading in the solution file correctly - does changing the objective function change the behaviour? Sounds a bit like a problem in that direction...