added initialstate_distribution for SimpleGridWorld

src/gridworld.jl

@@ -40,8 +40,20 @@ function POMDPs.stateindex(mdp::SimpleGridWorld, s::AbstractVector{Int})
     end
 end
 
-POMDPs.initialstate(mdp::SimpleGridWorld, rng::AbstractRNG) = GWPos(rand(rng, 1:mdp.size[1]), rand(rng, 1:mdp.size[2]))
+struct GWUniform
+    size::Tuple{Int, Int}
+end
+Base.rand(rng::AbstractRNG, d::GWUniform) = GWPos(rand(rng, 1:d.size[1]), rand(rng, 1:d.size[2]))
+function POMDPs.pdf(d::GWUniform, s::GWPos)
+    if all(1 .<= s[1] .<= d.size)
+        return 1/prod(d.size)
+    else
+        return 0.0
+    end
+end
+POMDPs.support(d::GWUniform) = (GWPos(x, y) for x in 1:d.size[1], y in 1:d.size[2])
 
+POMDPs.initialstate_distribution(mdp::SimpleGridWorld) = GWUniform(mdp.size)
 
 # Actions
 
@@ -55,7 +67,6 @@ const aind = Dict(:up=>1, :down=>2, :left=>3, :right=>4)
 POMDPs.actionindex(mdp::SimpleGridWorld, a::Symbol) = aind[a]
 
 
-
 # Transitions
 
 POMDPs.isterminal(m::SimpleGridWorld, s::AbstractVector{Int}) = any(s.<0)

test/simple_gridworld.jl

@@ -43,9 +43,17 @@ let
     POMDPModelTools.render(problem, stp, color=s->reward(problem,s))
     POMDPModelTools.render(problem, stp, color=s->rand())
     POMDPModelTools.render(problem, stp, color=s->"yellow")
+
+    ss = collect(states(problem))
+    isd = initialstate_distribution(problem)
+    for s in ss
+        if !isterminal(problem, s)
+            @test s in support(isd)
+            @test pdf(isd, s) > 0.0
+        end
+    end
 end
 
-# disabled until POMDPSimulators v0.1.2 is tagged
 let
     @nbinclude(joinpath(dirname(@__FILE__), "..", "notebooks", "GridWorld Visualization.ipynb"))
 end