use mutex for stats instead of yield at the end

src/population.rs

@@ -1,5 +1,6 @@
 
 use std::sync::Arc;
+use std::sync::Mutex;
 use std::thread;
 use crate::prelude::*;
 
@@ -78,7 +79,7 @@ impl Population {
         let len = humans.len();
 
         let mut humans_n_plus_1: Vec<Human> = Vec::with_capacity(len);
-        let mut stats: [i32; 4] = [0, 0, 0, 0];
+        let stats: [i32; 4] = [0, 0, 0, 0];
 
         let num_threads = num_threads.unwrap_or(1);
         if num_threads > 48 {
@@ -93,6 +94,8 @@ impl Population {
 
         let mut threads = vec![];
 
+        let stats_arc = Arc::new(Mutex::new(stats));
+
         for x in 0..num_threads {
 
             // find items to process
@@ -104,6 +107,7 @@ impl Population {
 
             // borrow copies of data for thread
             let humans = Arc::clone(&self.humans);
+            let stats = Arc::clone(&stats_arc);
             let (width, height, infection_rate, curing_rate, death_rate) = 
             (self.width, self.height, self.plague.infection_rate, self.plague.curing_rate, self.plague.death_rate);
 
@@ -112,7 +116,6 @@ impl Population {
                 // no write on data
                 // let humans = humans;
                 let mut humans_n_plus_1: Vec<Human> = Vec::with_capacity(num_items);
-                let mut stats: [i32; 4] = [0, 0, 0, 0];
 
                 for idx in lower_bound..upper_bound {
                     let human = &humans[idx];
@@ -120,7 +123,6 @@ impl Population {
                     let mut new_human = human.clone();
                     match human.present_state {
                         State::Normal => {
-                            stats[0] += 1;
                             let possible = [
                                 (human.x - 1, human.y - 1), (human.x, human.y - 1), (human.x + 1, human.y - 1),
                                 (human.x - 1, human.y)    ,                         (human.x + 1, human.y),
@@ -138,32 +140,43 @@ impl Population {
                                     None => {}
                                 }
                             }
+                            let mut stats = stats.lock().unwrap();
+                            stats[0] += 1;
                         }
                         State::Infected => {
-                            stats[1] += 1;
                             match die_or_cure(curing_rate, death_rate) {
                                 Some(x) => new_human.present_state = x,
                                 None => {}
                             }
+                            let mut stats = stats.lock().unwrap();
+                            stats[1] += 1;
+                        }
+                        State::Immune => {
+                            let mut stats = stats.lock().unwrap();
+                            stats[2] += 1;
+                        }
+                        State::Dead => {
+                            let mut stats = stats.lock().unwrap();
+                            stats[3] += 1;
                         }
-                        State::Immune => { stats[2] += 1; }
-                        State::Dead => { stats[3] += 1; }
                     }
                     humans_n_plus_1.push(new_human);
                 }
-                (humans_n_plus_1, stats)
+                (humans_n_plus_1,)
             }));
         }
 
         for t in threads {
             let mut res = t.join().unwrap();
             humans_n_plus_1.append(&mut res.0);
-            for x in 0..4 {
-                stats[x] += res.1[x];
-            }
+            // for x in 0..4 {
+            //     stats[x] += res.1[x];
+            // }
         }
 
         self.humans = Arc::new(humans_n_plus_1);
+        let stats = Arc::clone(&stats_arc);
+        let stats = *stats.lock().unwrap();
         stats
     }
 }
@@ -186,7 +199,7 @@ fn point_to_index(x: i32, y: i32, width: i32, height: i32) -> Option<usize> {
     }
 }
 
-pub fn roll(probability: i32) -> bool {
+fn roll(probability: i32) -> bool {
     if probability > 0 {
         let mut rng = rand::thread_rng();
         rng.gen_range(0..CORRECTED_PERCENTAGE) <= probability