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Quasi-Newton update rules issues #382
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I started looking a bit into these points. Ad 1) The function is used when updating the Hessian at Manopt.jl/src/solvers/quasi_Newton.jl Line 677 in 1856a26
or Manopt.jl/src/solvers/quasi_Newton.jl Line 738 in 1856a26
Ad 2) That might indeed be the case, I could only find the scale in the update of the full-matrix variants. Manopt.jl/src/solvers/quasi_Newton.jl Lines 514 to 516 in 1856a26
I am not sure where the scaling was “lost” in one of the reworks, but we can surely bring that back Ad 3) Sure, I am not 100% sure how to realise that, but when we have the iterate available doing a reset when that is zero sounds reasonable. When we wrote this code, reusing the state (and hence the updates) was not so much thought given to, for sure.
Manopt.jl/src/plans/quasi_newton_plan.jl Line 500 in 1856a26
and Manopt.jl/src/plans/quasi_newton_plan.jl Line 582 in 1856a26
which we basically have used before but then a bit more generic (not just a boolean)
and then
which might be a bit nicer to allow also for other ways to care for stability. |
I see, thanks.
I have it sketched already so I will only ask for a review when it's ready 🙂
Yes, unifying that is a good idea. |
If you see how to correctly add the scaling ( and unifying that to be a real value), feel free to add that as well. I am sure it was from one of the Wuang papers about QN. |
I'm currently working on some updates to quasi-Newton direction update rules. Here are a few things to check/consider:
QuasiNewtonCautiousDirectionUpdate
doesn't seem to useθ
function anywhere.QuasiNewtonLimitedMemoryDirectionUpdate
doesn't seem to usescale
.initialize_solver!
, and maybe also when the direction stops being a descent direction. That shouldn't happen for a well-designed set of options but it's a bit hard to tell which ones are safe from that issue.I'm also working on some variant of direction update for manifolds with corners inspired by L-BFGS-B. There are different approaches with elaborate line searches and update matrices but I'm aiming for something relatively simple and generic. I'm not aiming at competing with Fortran codes, my goal is making combined manifold-box constrained optimization work relatively well.
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