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Solving large sparse Ax=b with lower bound constraint

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Uanite on 11 Apr 2020
Commented: Uanite on 19 Apr 2020
I'm having some issues with some forward modelling I'm doing - im doing a forward model in a loop and currently solving an Ax=b system using a conjugate gradient least squares method (code from
My problem is that this solution is unconstrained, and so the solution converges close to the answer I expect, but has values outside permitted bounds still. If my constraint is say x >= c (c is a vector), is there a matlab inbuilt function that can do this?? I've tried lsqlin(A,b,[],[],[],[],c,[]) rather than the cgls function linked above, but the model no longer converges to a result that is even remotely correct.


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Accepted Answer

Torsten on 11 Apr 2020
Did you try starting from the solution of the unconstraint problem ?

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Uanite on 19 Apr 2020
Somehow missed that option, yep that helped it converge!

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