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This is an advanced setting just for allowing increased choices to power users that have problems with a given sketch and want to
test different flavours of DogLeg algorithm.
This commit does not change the default behaviour of FreeCAD. It is only intended to give more options to power users.
The advanced solver configuration is extended to support three different Gauss-newton steps for DogLeg:
FullPivLU => h_gn = Jx.fullPivLu().solve(-fx);
LeastNormFullPivLU => h_gn = Jx.adjoint()*(Jx*Jx.adjoint()).fullPivLu().solve(-fx);
LeastNormLdlt => h_gn = Jx.adjoint()*(Jx*Jx.adjoint()).ldlt().solve(-fx);
This setting is applied only to DogLeg. It is applied to DogLeg as normal or redundant solver, if DogLeg is the selected solver.
Selecting a solver different from DogLeg for both normal and redundant disables the setting.
We have been told:
https://forum.kde.org/viewtopic.php?f=74&t=129439#p346104
that our default Gauss-Newton step in DogLeg may not be adequate in general (we generally deal with underconstraint systems
unless we have a fully constraint sketch, and even then it is many times overconstraint at least for redundant solving).
We have been told that maybe these LeastNorm options are more suitable for us (performance set aside). This enables you as power
user to test if it works fine with FreeCAD.
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This commit sets the sketch size multiplier OFF by default (so the number of iterations DogLeg/BGFS/LM is not sketch size dependent).
In complicated sketches having a high number of parameters, with sketch multiplier on, the number of iterations is extremely high (100 parameters*100 iterations => 10000 iterations).
The idea of disabling this comes from tests performed by DeepSOIC and from my own experience using the Sketcher. In general
sketch multiplier makes FreeCAD unresposive (very high amount of iterations, not a real freeze) in big sketches so that users
end up killing the application. This is preventing the users from taking appropriate action, Developers from getting the information of the failure and
users angry.
The idea is that even for complicated sketchs N iterations (100 by default) should be enough to converge, if it is ever going to converge. Experience will tell us
if we have to increase this number in the range [100-300]. 100 iterations in complicated dossiers is in my experience generally under 30 seconds.
N.B.: This commit does not change the defaults stored in your computer, so if you have the sketcher multiplier on, the advanced solver dialog will still enforce this local setting. You
may disable it or click the "defaults" button to disable the sketcher multiplier.
