Need to check if the belief is terminal in stepthrough

[himanshugupta1009]

I believe there needs to be an additional check in the Base.iterate function here when the iterator is of type POMDPSimIterator -

POMDPs.jl/lib/POMDPTools/src/Simulators/stepthrough.jl

Line 85 in d837f16

if isterminal(it.pomdp, is[2]) || is[1] > it.max_steps

It is possible that the true state is not terminal, but the belief represented using a particle set consists of all terminal states. In that case, the simulation should stop, but this is not being checked at the moment and the action_info function leads to an error.

Please let me know if I am missing something here. Thanks!

[zsunberg]

The error here is due to an inaccurate belief. The person designing or operating the belief updater or policy should be responsible for handling this, not the simulation - it should be fixed at the solver/belief updater. If the simulator terminates on an inaccurate "terminal" belief, it could prevent the simulation from reaching an important terminal state, which would be a silent error and hence harmful.