DESPOTSolver(<keyword arguments>)

Implementation of the ARDESPOT solver trying to closely match the pseudo code of:

http://bigbird.comp.nus.edu.sg/m2ap/wordpress/wp-content/uploads/2017/08/jair14.pdf

Each field may be set via keyword argument. The fields that correspond to algorithm parameters match the definitions in the paper exactly.

Fields

• epsilon_0
• xi
• K
• D
• lambda
• T_max
• max_trials
• bounds
• default_action
• rng
• random_source
• bounds_warnings
• tree_in_info

Further information can be found in the field docstrings (e.g. ?DESPOTSolver.xi)

DefaultPolicyLB(policy; max_depth=nothing, final_value=(m,x)->0.0)
DefaultPolicyLB(solver; max_depth=nothing, final_value=(m,x)->0.0)

A lower bound calculated by running a default policy on the scenarios in a belief.

Keyword Arguments

• max_depth::Union{Nothing,Int}=nothing: max depth to run the simulation. The depth of the belief will be automatically subtracted so simulations for the bound will be run for max_depth-b.depth steps. If nothing, the solver's max depth will be used.
• final_value=(m,x)->0.0: a function (or callable object) that specifies an additional value to be added at the end of the simulation when max_depth is reached. This function will be called with two arguments, a POMDP, and a ScenarioBelief. It will not be called when the states in the belief are terminal.

IndependentBounds(lower, upper, check_terminal=false, consistency_fix_thresh=0.0)

Specify lower and upper bounds that are independent of each other (the most common case).

Keyword Arguments

• check_terminal::Bool=false: if true, then if all the states in the belief are terminal, the upper and lower bounds will be overridden and set to 0.
• consistency_fix_thresh::Float64=0.0: if upper < lower and upper >= lower-consistency_fix_thresh, then upper will be bumped up to lower.

Return a vector of lower bounds L of length lenb+lenba, with b nodes first followed by ba nodes.

Fill all the elements of the cache for b and children of b and return L[b]