Verify the LBFGSOperator update (push!)

[paraynaud]

Hello!

Context:

• I have to update several LBFGSOperator with differents (s,y) for a partitioned update PLBFGS.
• I cannot garantee that each (s,y) verify the cruvature condition.

I wonder if there is a way to see if push!(opLBFGS, s, y) performs the update or not.
I could check the curvature condition for each (s,y) on my side, but that would be a double check of the cruvature condition.

What are you thoughts?

[dpo]

We could reinstate this: https://github.com/JuliaSmoothOptimizers/LinearOperators.jl/blob/main/src/lbfgs.jl#L272

You can also use damping.