CornerProblem.hpp

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#ifndef AI_TOOLBOX_MDP_CORNER_PROBLEM_HEADER_FILE
#define AI_TOOLBOX_MDP_CORNER_PROBLEM_HEADER_FILE
 
#include <AIToolbox/MDP/Model.hpp>
#include <AIToolbox/MDP/Environments/Utils/GridWorld.hpp>
 
namespace AIToolbox::MDP {
    inline AIToolbox::MDP::Model makeCornerProblem(const GridWorld & grid, double stepUncertainty = 0.8) {
        using namespace GridWorldUtils;
 
        size_t S = grid.getWidth() * grid.getHeight();
        size_t A = 4;
 
        AIToolbox::DumbMatrix3D transitions(boost::extents[S][A][S]);
        AIToolbox::DumbMatrix3D rewards(boost::extents[S][A][S]);
 
        for ( size_t x = 0; x < grid.getWidth(); ++x ) {
            for ( size_t y = 0; y < grid.getHeight(); ++y ) {
                auto s = grid(x,y);
                if ( s == 0 || s == S-1 ) {
                    // Self absorbing states
                    for ( size_t a = 0; a < A; ++a )
                        transitions[s][a][s] = 1.0;
                }
                else {
                    for ( size_t a = 0; a < A; ++a ) {
                        auto s1 = grid.getAdjacent((Direction)a, s);
                        // If the move takes you outside the map, it doesn't do
                        // anything
                        if ( s == s1 ) transitions[s][a][s1] = 1.0;
                        else {
                            transitions[s][a][s1] = stepUncertainty;
                            transitions[s][a][s] = 1.0 - stepUncertainty;
                        }
                        rewards[s][a][s1] = -1.0;
                    }
                }
            }
        }
        return Model(S, A, transitions, rewards, 0.95);
    }
}
 
#endif