% JCR_EXAMPLE - for the jacks car rental example.
% 
% See ePage 262 in the Sutton book.
% 
% Written by:
% -- 
% John L. Weatherwax                2007-12-03
% 
% email: wax@alum.mit.edu
% 
% Please send comments and especially bug reports to the
% above email address.
% 
%-----

clc; 
close all; 

gamma = 0.9; 
  
% the maximum number of cars we can store (overnight) at each site: 
max_n_cars = 20; 
%max_n_cars = 10; 
%max_n_cars = 5; 

max_num_cars_can_transfer = 5; 

% the parameters of the environment: 
if( 0 ) 
  lambda_A_return = 3; % a debugging case: 
  lambda_A_rental = 3; 
  lambda_B_return = 3; 
  lambda_B_rental = 3; 
else
  lambda_A_return = 3; 
  lambda_A_rental = 3; 
  lambda_B_return = 2; 
  lambda_B_rental = 4; 
end

% precompute the rewards and transition probabilities: 
[Ra,Pa] = cmpt_P_and_R(lambda_A_rental,lambda_A_return,max_n_cars,max_num_cars_can_transfer);
[Rb,Pb] = cmpt_P_and_R(lambda_B_rental,lambda_B_return,max_n_cars,max_num_cars_can_transfer);

% initial state value function: 
V = zeros(max_n_cars+1,max_n_cars+1); 

% initial policy: 
pol_pi = zeros(max_n_cars+1,max_n_cars+1); 

policyStable = 0; iterNum = 0; 
while( ~policyStable )
  % plot the current policy:
  if( iterNum~=0 ) 
    figure; imagesc( 0:max_n_cars, 0:max_n_cars, pol_pi ); colorbar; xlabel( 'num at B' ); ylabel( 'num at A' ); 
    title( ['current policy iter=', num2str(iterNum)] ); axis xy; drawnow;
    %fn=sprintf('policy_iter_%d.eps',iterNum); saveas( gcf, fn, 'eps2' ); 
  end
  
  % evaluate the state-value function under this policy: 
  V = jcr_policy_evaluation(V,pol_pi,gamma,Ra,Pa,Rb,Pb,max_num_cars_can_transfer);
  figure; imagesc( 0:max_n_cars, 0:max_n_cars, V ); colorbar; 
  xlabel( 'num at B' ); ylabel( 'num at A' ); 
  title( ['current state-value function iter=', num2str(iterNum)] ); axis xy; drawnow; 
  %fn=sprintf('state_value_fn_iter_%d.eps',iterNum); saveas( gcf, fn, 'eps2' ); 
  
  % compute an improved policy using the most recent as a base: 
  [pol_pi,policyStable] = jcr_policy_improvement(pol_pi,V,gamma,Ra,Pa,Rb,Pb,max_num_cars_can_transfer);
  
  iterNum=iterNum+1; 
  %if( iterNum==2 ) break; end; 
end
% plot the current policy:
%figure; imagesc( pol_pi ); colorbar; title( ['current policy iter=', num2str(iterNum)] ); drawnow;