Non-deterministic task ordering in KinematicsSolver

[imwhocodes]

KinematicsSolver stores tasks and constraints in:

std::set<Task*> tasks;
std::set<Constraint*> constraints;

Since these sets are ordered by pointer value, iteration order can differ between processes or executions even when tasks are created in the same logical order.

This ordering propagates to QP construction.

I observed this while running identical IK requests in multiple worker processes: the final results differed slightly depending on which PID performed the solve. The difference was small (around 1e-8 after many iterations), and appears consistent with numerical differences caused by different QP assembly order.

It would be useful for task/constraint iteration, and therefore QP construction, to be deterministic independently of memory allocation addresses.

Thank you for this amazing project,
Luca

[Gregwar]

Hello,

I've switched containers to vector instead of sets. It only comes with a higher cost to remove items, but this can be neglected and happens rarely.

It should make the problem construction order deterministic

[Gregwar]

Released v0.9.24 which includes this fix (build in progress)