Added automatic stopping for MonteCarloReward

reCTBN/src/parameter_learning.rs

@@ -144,9 +144,7 @@ impl ParameterLearning for BayesianApproach {
             .zip(M.mapv(|x| x as f64).axis_iter(Axis(2)))
             .for_each(|(mut C, m)| C.assign(&(&m.mapv(|y| y + alpha) / &T.mapv(|y| y + tau))));
 
-
-        CIM.outer_iter_mut()
-            .for_each(|mut C| {
+        CIM.outer_iter_mut().for_each(|mut C| {
             C.diag_mut().fill(0.0);
         });
 

reCTBN/src/reward.rs

@@ -1,5 +1,5 @@
-pub mod reward_function;
 pub mod reward_evaluation;
+pub mod reward_function;
 
 use std::collections::HashMap;
 

reCTBN/src/reward/reward_evaluation.rs

@@ -1,11 +1,11 @@
 use std::collections::HashMap;
 
 use rayon::prelude::{IntoParallelIterator, ParallelIterator};
+use statrs::distribution::ContinuousCDF;
 
 use crate::params::{self, ParamsTrait};
 use crate::process;
 
-
 use crate::{
     process::NetworkProcessState,
     reward::RewardEvaluation,
@@ -18,7 +18,9 @@ pub enum RewardCriteria {
 }
 
 pub struct MonteCarloReward {
-    n_iterations: usize,
+    max_iterations: usize,
+    max_err_stop: f64,
+    alpha_stop: f64,
     end_time: f64,
     reward_criteria: RewardCriteria,
     seed: Option<u64>,
@@ -26,13 +28,17 @@ pub struct MonteCarloReward {
 
 impl MonteCarloReward {
     pub fn new(
-        n_iterations: usize,
+        max_iterations: usize,
+        max_err_stop: f64,
+        alpha_stop: f64,
         end_time: f64,
         reward_criteria: RewardCriteria,
         seed: Option<u64>,
     ) -> MonteCarloReward {
         MonteCarloReward {
-            n_iterations,
+            max_iterations,
+            max_err_stop,
+            alpha_stop,
             end_time,
             reward_criteria,
             seed,
@@ -58,7 +64,8 @@ impl RewardEvaluation for MonteCarloReward {
 
         let n_states: usize = variables_domain.iter().map(|x| x.len()).product();
 
-        (0..n_states).into_par_iter()
+        (0..n_states)
+            .into_par_iter()
             .map(|s| {
                 let state: process::NetworkProcessState = variables_domain
                     .iter()
@@ -85,10 +92,13 @@ impl RewardEvaluation for MonteCarloReward {
     ) -> f64 {
         let mut sampler =
             ForwardSampler::new(network_process, self.seed.clone(), Some(state.clone()));
-        let mut ret = 0.0;
+        let mut expected_value = 0.0;
+        let mut squared_expected_value = 0.0;
+        let normal = statrs::distribution::Normal::new(0.0, 1.0).unwrap();
 
-        for _i in 0..self.n_iterations {
+        for i in 0..self.max_iterations {
             sampler.reset();
+            let mut ret = 0.0;
             let mut previous = sampler.next().unwrap();
             while previous.t < self.end_time {
                 let current = sampler.next().unwrap();
@@ -121,14 +131,31 @@ impl RewardEvaluation for MonteCarloReward {
                 }
                 previous = current;
             }
+
+            let float_i = i as f64;
+            expected_value =
+                expected_value * float_i as f64 / (float_i + 1.0) + ret / (float_i + 1.0);
+            squared_expected_value = squared_expected_value * float_i as f64 / (float_i + 1.0)
+                + ret.powi(2) / (float_i + 1.0);
+
+            if i > 2 {
+                let var =
+                    (float_i + 1.0) / float_i * (squared_expected_value - expected_value.powi(2));
+                if self.alpha_stop
+                    - 2.0 * normal.cdf(-(float_i + 1.0).sqrt() * self.max_err_stop / var.sqrt())
+                    > 0.0
+                {
+                    return expected_value;
+                }
+            }
         }
 
-        ret / self.n_iterations as f64
+        expected_value
     }
 }
 
 pub struct NeighborhoodRelativeReward<RE: RewardEvaluation> {
-    inner_reward: RE
+    inner_reward: RE,
 }
 
 impl<RE: RewardEvaluation> NeighborhoodRelativeReward<RE> {
@@ -143,22 +170,28 @@ impl<RE:RewardEvaluation> RewardEvaluation for NeighborhoodRelativeReward<RE> {
         network_process: &N,
         reward_function: &R,
     ) -> HashMap<process::NetworkProcessState, f64> {
-
-        let absolute_reward = self.inner_reward.evaluate_state_space(network_process, reward_function);
+        let absolute_reward = self
+            .inner_reward
+            .evaluate_state_space(network_process, reward_function);
 
         //This approach optimize memory. Maybe optimizing execution time can be better.
-        absolute_reward.iter().map(|(k1, v1)| {
+        absolute_reward
+            .iter()
+            .map(|(k1, v1)| {
                 let mut max_val: f64 = 1.0;
                 absolute_reward.iter().for_each(|(k2, v2)| {
-                let count_diff:usize = k1.iter().zip(k2.iter()).map(|(s1, s2)| if s1 == s2 {0} else {1}).sum();
+                    let count_diff: usize = k1
+                        .iter()
+                        .zip(k2.iter())
+                        .map(|(s1, s2)| if s1 == s2 { 0 } else { 1 })
+                        .sum();
                     if count_diff < 2 {
                         max_val = max_val.max(v1 / v2);
                     }
-            
                 });
                 (k1.clone(), max_val)
-        }).collect()
-        
+            })
+            .collect()
     }
 
     fn evaluate_state<N: process::NetworkProcess, R: super::RewardFunction>(

reCTBN/tests/reward_evaluation.rs

@@ -33,7 +33,7 @@ fn simple_factored_reward_function_binary_node_MC() {
     let s0: NetworkProcessState = vec![params::StateType::Discrete(0)];
     let s1: NetworkProcessState = vec![params::StateType::Discrete(1)];
 
-    let mc = MonteCarloReward::new(100, 10.0, RewardCriteria::InfiniteHorizon { discount_factor: 1.0 }, Some(215));
+    let mc = MonteCarloReward::new(10000, 1e-1, 1e-1, 10.0, RewardCriteria::InfiniteHorizon { discount_factor: 1.0 }, Some(215));
     assert_abs_diff_eq!(3.0, mc.evaluate_state(&net, &rf, &s0), epsilon = 1e-2);
     assert_abs_diff_eq!(3.0, mc.evaluate_state(&net, &rf, &s1), epsilon = 1e-2);
     
@@ -42,7 +42,7 @@ fn simple_factored_reward_function_binary_node_MC() {
     assert_abs_diff_eq!(3.0, rst[&s1], epsilon = 1e-2);
 
 
-    let mc = MonteCarloReward::new(100, 10.0, RewardCriteria::FiniteHorizon, Some(215));
+    let mc = MonteCarloReward::new(10000, 1e-1, 1e-1, 10.0, RewardCriteria::FiniteHorizon, Some(215));
     assert_abs_diff_eq!(30.0, mc.evaluate_state(&net, &rf, &s0), epsilon = 1e-2);
     assert_abs_diff_eq!(30.0, mc.evaluate_state(&net, &rf, &s1), epsilon = 1e-2);
     
@@ -113,7 +113,7 @@ fn simple_factored_reward_function_chain_MC() {
         params::StateType::Discrete(0),
     ];
 
-    let mc = MonteCarloReward::new(1000, 10.0, RewardCriteria::InfiniteHorizon { discount_factor: 1.0 }, Some(215));
+    let mc = MonteCarloReward::new(10000, 1e-1, 1e-1, 10.0, RewardCriteria::InfiniteHorizon { discount_factor: 1.0 }, Some(215));
     assert_abs_diff_eq!(2.447, mc.evaluate_state(&net, &rf, &s000), epsilon = 1e-1);
 
     let rst = mc.evaluate_state_space(&net, &rf);