use mutex for stats instead of yield at the end

remove const

no need for RwLock as we don't use mut in thread \o/

Cargo.lock

@@ -2,18 +2,74 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "atty"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "winapi",
+]
+
 [[package]]
 name = "autocfg"
 version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
 
+[[package]]
+name = "bitflags"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
 [[package]]
 name = "cfg-if"
 version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
+[[package]]
+name = "clap"
+version = "3.1.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85a35a599b11c089a7f49105658d089b8f2cf0882993c17daf6de15285c2c35d"
+dependencies = [
+ "atty",
+ "bitflags",
+ "clap_derive",
+ "clap_lex",
+ "indexmap",
+ "lazy_static",
+ "strsim",
+ "termcolor",
+ "textwrap",
+]
+
+[[package]]
+name = "clap_derive"
+version = "3.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a3aab4734e083b809aaf5794e14e756d1c798d2c69c7f7de7a09a2f5214993c1"
+dependencies = [
+ "heck",
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "clap_lex"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a37c35f1112dad5e6e0b1adaff798507497a18fceeb30cceb3bae7d1427b9213"
+dependencies = [
+ "os_str_bytes",
+]
+
 [[package]]
 name = "console"
 version = "0.15.0"
@@ -52,6 +108,21 @@ version = "0.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d7afe4a420e3fe79967a00898cc1f4db7c8a49a9333a29f8a4bd76a253d5cd04"
 
+[[package]]
+name = "heck"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2540771e65fc8cb83cd6e8a237f70c319bd5c29f78ed1084ba5d50eeac86f7f9"
+
+[[package]]
+name = "hermit-abi"
+version = "0.1.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62b467343b94ba476dcb2500d242dadbb39557df889310ac77c5d99100aaac33"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "indexmap"
 version = "1.6.2"
@@ -62,6 +133,12 @@ dependencies = [
  "hashbrown",
 ]
 
+[[package]]
+name = "lazy_static"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+
 [[package]]
 name = "libc"
 version = "0.2.124"
@@ -74,6 +151,12 @@ version = "1.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "87f3e037eac156d1775da914196f0f37741a274155e34a0b7e427c35d2a2ecb9"
 
+[[package]]
+name = "os_str_bytes"
+version = "6.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e22443d1643a904602595ba1cd8f7d896afe56d26712531c5ff73a15b2fbf64"
+
 [[package]]
 name = "parameterized"
 version = "1.0.0"
@@ -101,6 +184,30 @@ version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "eb9f9e6e233e5c4a35559a617bf40a4ec447db2e84c20b55a6f83167b7e57872"
 
+[[package]]
+name = "proc-macro-error"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
+dependencies = [
+ "proc-macro-error-attr",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro-error-attr"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "version_check",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.37"
@@ -168,11 +275,18 @@ checksum = "f497285884f3fcff424ffc933e56d7cbca511def0c9831a7f9b5f6153e3cc89b"
 name = "rusty_propagation"
 version = "0.1.0"
 dependencies = [
+ "clap",
  "console",
  "parameterized",
  "rand",
 ]
 
+[[package]]
+name = "strsim"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
+
 [[package]]
 name = "syn"
 version = "1.0.92"
@@ -184,6 +298,15 @@ dependencies = [
  "unicode-xid",
 ]
 
+[[package]]
+name = "termcolor"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bab24d30b911b2376f3a13cc2cd443142f0c81dda04c118693e35b3835757755"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "terminal_size"
 version = "0.1.17"
@@ -194,6 +317,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "textwrap"
+version = "0.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b1141d4d61095b28419e22cb0bbf02755f5e54e0526f97f1e3d1d160e60885fb"
+
 [[package]]
 name = "unicode-width"
 version = "0.1.9"
@@ -206,6 +335,12 @@ version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "957e51f3646910546462e67d5f7599b9e4fb8acdd304b087a6494730f9eebf04"
 
+[[package]]
+name = "version_check"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
+
 [[package]]
 name = "wasi"
 version = "0.10.2+wasi-snapshot-preview1"
@@ -228,6 +363,15 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 
+[[package]]
+name = "winapi-util"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "70ec6ce85bb158151cae5e5c87f95a8e97d2c0c4b001223f33a334e3ce5de178"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "winapi-x86_64-pc-windows-gnu"
 version = "0.4.0"

Cargo.toml

@@ -7,3 +7,4 @@ edition = "2021"
 console = "0.15.0" 
 rand = "0.8.5" 
 parameterized = "1.0.0"
+clap = { version = "3.1.15", features = ["derive"] }

src/main.rs

@@ -12,14 +12,34 @@ mod prelude {
 }
 
 use prelude::*;
+use clap::Parser;
+use std::time::Instant;
+
+#[derive(Parser, Debug)]
+struct Args {
+    /// Number of threads
+    #[clap(short, long, default_value_t = 1)]
+    threads: usize,
+    /// Display stats after each propagation
+    #[clap(short, long)]
+    display: bool,
+    /// Width of humans grid in population
+    #[clap(short, long, default_value_t = 1000)]
+    width: i32,
+    /// Height of humans grid in population
+    #[clap(short, long, default_value_t = 1000)]
+    height: i32,
+}
 
 fn main() {
+    let args = Args::parse();
+
     let term = Term::stdout();
     term.write_line("********** Rusty Propagation (Console) 2022 **********")
         .expect("Oops Looks like we have a problem here...");
 
     let disease = Disease::new(20, 10, 5, String::from("Covid 44"));
-    let mut population = Population::new(20, 10, 5, 1000, 1000, disease);
+    let mut population = Population::new(20,10,5,args.width,args.height,disease);
     //population.change_disease(disease);
     println!("After Filling");
     //population.display();
@@ -27,18 +47,21 @@ fn main() {
     let mut stats: [i32; 4];
     // = [0,0,0,0];
     let mut counter: u32 = 0;
+    let now = Instant::now();
     loop {
         counter += 1;
-        stats = population.propagate();
+        stats = population.propagate_new(Some(args.threads));
         //population.display();
-        println!(
-            "Normal: {} Infecteds: {} Immunes: {} Deads: {}",
-            stats[0], stats[1], stats[2], stats[3]
-        );
+        if args.display {
+            println!(
+                "Normal: {} Infecteds: {} Immunes: {} Deads: {}",
+                stats[0], stats[1], stats[2], stats[3]
+            );
+        }
         if stats[1] == 0 {
             break;
         }
     }
-    println!("Propagation finished in {} steps", counter);
+    println!("Propagation finished in {} steps, {:?}", counter, now.elapsed());
     //population.display();
 }

src/population.rs

@@ -1,16 +1,14 @@
-use crate::prelude::*;
 
-#[derive(Debug)]
-pub struct Point {
-    x: i32,
-    y: i32,
-}
+use std::sync::Arc;
+use std::sync::Mutex;
+use std::thread;
+use crate::prelude::*;
 
 pub struct Population {
     pub start_infected_ratio: i32,
     pub start_immune_ratio: i32,
     pub start_dead_ratio: i32,
-    pub humans: Vec<Human>,
+    pub humans: Arc<Vec<Human>>,
     pub width: i32,
     pub height: i32,
     pub age: i32,
@@ -71,197 +69,137 @@ impl Population {
             height: height,
             plague: plague,
             age: 0,
-            humans: the_humans,
+            humans: Arc::new(the_humans),
             size: size,
         }
     }
-    // pub fn change_disease(&mut self, plague:Disease){
-    //     self.plague = plague;
-    // }
 
-    fn is_inside(&self, pos: &Point) -> bool {
-        if pos.x >= 0 && pos.x < self.width && pos.y >= 0 && pos.y < self.height {
-            true
-        } else {
-            false
+    pub fn propagate_new(&mut self, num_threads: Option<usize>) -> [i32; 4] {
+        let humans = Arc::clone(&self.humans);
+        let len = humans.len();
+
+        let mut humans_n_plus_1: Vec<Human> = Vec::with_capacity(len);
+        let stats: [i32; 4] = [0, 0, 0, 0];
+
+        let num_threads = num_threads.unwrap_or(1);
+        if num_threads > 48 {
+            panic!("too many threads")
         }
-    }
 
-    fn is_inside_and_infected(&self, point: Point) -> bool {
-        if self.is_inside(&point) {
-            let idx = human_idx(point.x, point.y, self.width);
-            if self.humans[idx].present_state == State::Infected {
-                roll(self.plague.infection_rate)
-            } else {
-                false
-            }
-        } else {
-            false
+        // number of items per batch
+        let mut num_items = (len / num_threads) as usize;
+        if len % num_threads != 0 {
+            num_items += 1;
         }
-    }
 
-    pub fn propagate(&mut self) -> [i32; 4] {
-        let mut people_to_check: Vec<Point> =
-            Vec::with_capacity(self.size);
-        let mut possible_infected: Vec<Point> =
-            Vec::with_capacity(self.size);
-        let mut people_to_infect: Vec<Point> =
-            Vec::with_capacity(self.size);
-        let mut people_to_cure: Vec<Point> =
-            Vec::with_capacity(self.size);
-        let mut people_to_kill: Vec<Point> =
-            Vec::with_capacity(self.size);
-        let mut stats: [i32; 4] = [0, 0, 0, 0];
-        // stats[0] Normal stats[1] Infected stats[2] Immune stats[3] Dead
+        let mut threads = vec![];
 
-        for h in self.humans.iter() {
-            match h.present_state {
-                State::Normal => {
-                    possible_infected.push(Point{ x: h.x, y: h.y});
-                    stats[0] += 1;
+        let stats_arc = Arc::new(Mutex::new(stats));
+
+        for x in 0..num_threads {
+
+            // find items to process
+            let lower_bound = x * num_items;
+            let mut upper_bound = (x + 1) * num_items;
+            if upper_bound > len {
+                upper_bound = len;
+            };
+
+            // 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);
+
+            threads.push(thread::spawn(move || {
+
+                // no write on data
+                // let humans = humans;
+                let mut humans_n_plus_1: Vec<Human> = Vec::with_capacity(num_items);
+
+                for idx in lower_bound..upper_bound {
+                    let human = &humans[idx];
+                    // let mut neighbors: Vec<&Human> = Vec::with_capacity(8);
+                    let mut new_human = human.clone();
+                    match human.present_state {
+                        State::Normal => {
+                            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),
+                                (human.x - 1, human.y + 1), (human.x, human.y + 1), (human.x + 1, human.y + 1),
+                            ];
+                            for neigh_coords in possible.iter() {
+                                let neigh_idx = point_to_index(neigh_coords.0, neigh_coords.1, width, height);
+                                match neigh_idx {
+                                    Some(x) => if humans[x].present_state == State::Infected {
+                                        if roll(infection_rate) {
+                                            new_human.present_state = State::Infected;
+                                            break;
+                                        }
+                                    }
+                                    None => {}
+                                }
+                            }
+                            let mut stats = stats.lock().unwrap();
+                            stats[0] += 1;
+                        }
+                        State::Infected => {
+                            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;
+                        }
+                    }
+                    humans_n_plus_1.push(new_human);
                 }
-                State::Infected => {
-                    people_to_check.push(Point { x: h.x, y: h.y });
-                    stats[1] += 1;
-                }
-                State::Immune => {
-                    stats[2] += 1;
-                }
-                State::Dead => {
-                    stats[3] += 1;
-                }
-            }
-        }
-        //        for pos in &people_to_check {
-        for pos in people_to_check.iter() {
-            //people_to_check.iter().map(|pos|{
-            //get all the other people next to me and check if i die cure or infect
-            //now we can start to check if people would be infected or not
-            //let idx = human_idx(pos.x as i32, pos.y as i32, self.width as i32);
-            if roll(self.plague.curing_rate) {
-                //checks if the man recovers
-                people_to_cure.push(Point { x: pos.x, y: pos.y });
-            } else {
-                if roll(self.plague.death_rate) {
-                    //cheks if the man dies
-                    people_to_kill.push(Point { x: pos.x, y: pos.y });
-                }
-            }
-        }
-        for pos in possible_infected.iter() {
-            let infected: bool = self.is_inside_and_infected(
-                Point {
-                    x: pos.x - 1,
-                    y: pos.y - 1,
-                },
-            ) || //Top Left
-            self.is_inside_and_infected(
-                Point {
-                    x: pos.x,
-                    y: pos.y - 1,
-                },
-            ) || //Top
-            self.is_inside_and_infected(
-                Point {
-                    x: pos.x + 1,
-                    y: pos.y - 1,
-                },
-            ) || //Top Right
-            self.is_inside_and_infected(
-                Point {
-                    x: pos.x - 1,
-                    y: pos.y,
-                },
-            ) || //Left
-            self.is_inside_and_infected(
-                Point {
-                    x: pos.x + 1,
-                    y: pos.y,
-                },
-            ) || //Right
-            self.is_inside_and_infected(
-                Point {
-                    x: pos.x - 1,
-                    y: pos.y + 1,
-                },
-            ) || //Bottom Left
-            self.is_inside_and_infected(
-                Point {
-                    x: pos.x,
-                    y: pos.y + 1,
-                },
-            ) || //Bottom
-            self.is_inside_and_infected(
-                Point {
-                    x: pos.x + 1,
-                    y: pos.y + 1,
-                },
-            ); //Bottom Right
-            if infected {
-                people_to_infect.push(Point { x: pos.x, y: pos.y });
-            }
+                (humans_n_plus_1,)
+            }));
         }
 
-        for infected_position in people_to_infect.iter() {
-            // println!("To infect: {:?}", infected_position);
-            //people_to_infect.iter().map(|infected_position|{
-            let infected_index = human_idx(infected_position.x, infected_position.y, self.width);
-            // let _ = infected_position.x;
-            //DEBUG
-            //println!("x: {} y: {} index: {}",infected_position.x,infected_position.y,infected_index);
-            self.humans[infected_index].present_state = State::Infected;
-            //DEBUG
-            //println!("Infected someone");
+        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 cured_position in people_to_cure.iter() {
-            //people_to_cure.iter().map(|cured_position|{
-            let cured_index = human_idx(cured_position.x, cured_position.y, self.width);
-            if self.humans[cured_index].present_state != State::Infected {
-                println!("not infected");
-            }
-            self.humans[cured_index].present_state = State::Immune;
-            //DEBUG
-            //println!("Cured someone");
-        }
-
-        for dead_position in people_to_kill.iter() {
-            //people_to_kill.iter().map(|dead_position|{
-            let dead_index = human_idx(dead_position.x, dead_position.y, self.width);
-            if self.humans[dead_index].present_state == State::Dead {
-                // println!("Already dead");
-            } else {
-                self.humans[dead_index].present_state = State::Dead;
-            }
-            //DEBUG
-        }
-        assert_eq!(
-            stats[0] + stats[1] + stats[2] + stats[3],
-            self.size as i32
-        );
+        self.humans = Arc::new(humans_n_plus_1);
+        let stats = Arc::clone(&stats_arc);
+        let stats = *stats.lock().unwrap();
         stats
     }
-
-    // pub fn display(&mut self){
-    //     let sprite = "#";
-    //     print!("\n");
-    //     for x in 0..self.width{
-    //         for y in 0..self.height{
-    //             let index = human_idx(x as i32,y as i32,self.width as i32);
-    //             match self.humans[index].present_state {
-    //                 State::Normal => print!("{}",style(sprite).green()),
-    //                 State::Dead => print!("{}",style(sprite).black()),
-    //                 State::Infected => print!("{}",style(sprite).red()),
-    //                 State::Immune => print!("{}",style(sprite).blue()),
-    //                 _ => print!("{}",style(sprite).white()),
-    //             }
-    //         }
-    //         print!("\n");
-    //     }
-    // }
 }
 
-pub fn roll(probability: i32) -> bool {
+fn die_or_cure(curing_rate: i32, death_rate: i32) -> Option<State> {
+    if roll(curing_rate) {
+        Some(State::Immune)
+    } else if roll(death_rate) {
+        Some(State::Dead)
+    } else {
+        None
+    }
+}
+
+fn point_to_index(x: i32, y: i32, width: i32, height: i32) -> Option<usize> {
+    if (x >= 0) && (x < width) && (y >= 0) && (y < height) {
+        Some(human_idx(x, y, width))
+    } else {
+        None
+    }
+}
+
+fn roll(probability: i32) -> bool {
     if probability > 0 {
         let mut rng = rand::thread_rng();
         rng.gen_range(0..CORRECTED_PERCENTAGE) <= probability
@@ -275,6 +213,8 @@ mod tests {
     use super::*;
     use parameterized::parameterized;
 
+    const THREADS: Option<usize> = Some(4);
+
     #[derive(Debug)]
     struct Stats {
         normal: i32,
@@ -363,14 +303,14 @@ mod tests {
     fn population_new() {
         let disease = Disease::new(20, 10, 5, String::from("Covid 44"));
         let (width, height) = (5, 7);
-        let population = Population::new(20, 10, 5, 5, 7, disease);
-        assert_eq!(population.humans.len(), 5 * 7);
-        for h in population.humans.iter() {
+        let population = Population::new(20, 10, 5, width, height, disease);
+        let humans = Arc::clone(&population.humans);
+        assert_eq!(humans.len(), 5 * 7);
+        for h in humans.iter() {
             let idx = human_idx(h.x, h.y, width);
-            assert_eq!(population.humans[idx].x, h.x, "coordinates should match");
-            assert_eq!(population.humans[idx].y, h.y, "coordinates should match");
+            assert_eq!(humans[idx].x, h.x, "coordinates should match");
+            assert_eq!(humans[idx].y, h.y, "coordinates should match");
         }
-        assert_eq!(population.humans.len(), (width * height) as usize);
     }
 
     #[test]
@@ -379,7 +319,8 @@ mod tests {
         let (width, height) = (5, 7);
         let population = Population::new(20, 10, 5, 5, 7, disease);
 
-        let stats: Stats = humans_stats(&population.humans);
+        let humans = Arc::clone(&population.humans);
+        let stats: Stats = humans_stats(&humans);
         println!("Stats: {:?}", stats);
 
         assert_eq!(
@@ -397,25 +338,29 @@ mod tests {
 
         disease = Disease::new(0, 0, 0, String::from("Test"));
         population = Population::new(0, 0, 0, width, height, disease);
-        stats = humans_stats(&population.humans);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("should be normal: {:?}", stats);
         assert_eq!(stats.normal, width * height);
 
         disease = Disease::new(0, 0, 0, String::from("Test"));
         population = Population::new(100, 0, 0, width, height, disease);
-        stats = humans_stats(&population.humans);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("should be infected: {:?}", stats);
         assert_eq!(stats.infected, width * height);
 
         disease = Disease::new(0, 0, 0, String::from("Test"));
         population = Population::new(0, 100, 0, width, height, disease);
-        stats = humans_stats(&population.humans);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("should be immune: {:?}", stats);
         assert_eq!(stats.immune, width * height);
 
         disease = Disease::new(0, 0, 0, String::from("Test"));
         population = Population::new(0, 0, 100, width, height, disease);
-        stats = humans_stats(&population.humans);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("should be dead: {:?}", stats);
         assert_eq!(stats.dead, width * height);
     }
@@ -441,13 +386,15 @@ mod tests {
         let mut propagate_stats: [i32; 4];
 
         // infect every one
-        stats = humans_stats(&population.humans);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("stats after init: {:?}", stats);
         assert_eq!(stats.infected, 100, "everybody should be infected");
 
         // kill every one
-        propagate_stats = population.propagate();
-        stats = humans_stats(&population.humans);
+        propagate_stats = population.propagate_new(THREADS);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("propate_stats: {:?}", propagate_stats);
         assert_eq!(propagate_stats, [0, 100, 0, 0]);
         assert_eq!(stats.normal, 0);
@@ -456,8 +403,9 @@ mod tests {
         assert_eq!(stats.dead, 100);
 
         for _x in 0..100 {
-            propagate_stats = population.propagate();
-            stats = humans_stats(&population.humans);
+            propagate_stats = population.propagate_new(THREADS);
+            let humans = Arc::clone(&population.humans);
+            stats = humans_stats(&humans);
             println!("propate_stats: {:?}", propagate_stats);
             assert_eq!(propagate_stats, [0, 0, 0, 100]);
             assert_eq!(stats.normal, 0);
@@ -475,7 +423,7 @@ mod tests {
         let mut propagate_stats: [i32; 4];
 
         // start with normal population
-        population.humans = vec![
+        population.humans = Arc::new(vec![
             Human {
                 present_state: State::Normal,
                 x: 0,
@@ -521,14 +469,16 @@ mod tests {
                 x: 2,
                 y: 2,
             },
-        ];
-        stats = humans_stats(&population.humans);
+        ]);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("stats after init: {:?}", stats);
         assert_eq!(stats.normal, 8);
 
         // kill every one
-        propagate_stats = population.propagate();
-        stats = humans_stats(&population.humans);
+        propagate_stats = population.propagate_new(THREADS);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("propate_stats: {:?}", propagate_stats);
         assert_eq!(propagate_stats, [8, 1, 0, 0]);
         assert_eq!(stats.normal, 0);
@@ -537,8 +487,9 @@ mod tests {
         assert_eq!(stats.dead, 0);
 
         for _x in 0..100 {
-            propagate_stats = population.propagate();
-            stats = humans_stats(&population.humans);
+            propagate_stats = population.propagate_new(THREADS);
+            let humans = Arc::clone(&population.humans);
+            stats = humans_stats(&humans);
             println!("propate_stats: {:?}", propagate_stats);
             assert_eq!(propagate_stats, [0, 9, 0, 0]);
             assert_eq!(stats.normal, 0);
@@ -556,7 +507,7 @@ mod tests {
         let mut propagate_stats: [i32; 4];
 
         // start with normal population
-        population.humans = vec![
+        population.humans = Arc::new(vec![
             Human {
                 present_state: State::Normal,
                 x: 0,
@@ -602,14 +553,16 @@ mod tests {
                 x: 2,
                 y: 2,
             },
-        ];
-        stats = humans_stats(&population.humans);
+        ]);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("stats after init: {:?}", stats);
         assert_eq!(stats.normal, 8);
 
         // infect every one
-        propagate_stats = population.propagate();
-        stats = humans_stats(&population.humans);
+        propagate_stats = population.propagate_new(THREADS);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("propate_stats: {:?}", propagate_stats);
         println!("population: {:?}", stats);
         assert_eq!(propagate_stats, [8, 1, 0, 0]);
@@ -619,8 +572,9 @@ mod tests {
         assert_eq!(stats.dead, 0);
 
         // cure every one
-        propagate_stats = population.propagate();
-        stats = humans_stats(&population.humans);
+        propagate_stats = population.propagate_new(THREADS);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("propate_stats: {:?}", propagate_stats);
         println!("population: {:?}", stats);
         assert_eq!(propagate_stats, [0, 8, 1, 0]);
@@ -631,8 +585,9 @@ mod tests {
 
         // then
         for _x in 0..100 {
-            propagate_stats = population.propagate();
-            stats = humans_stats(&population.humans);
+            propagate_stats = population.propagate_new(THREADS);
+            let humans = Arc::clone(&population.humans);
+            stats = humans_stats(&humans);
             println!("propate_stats: {:?}", propagate_stats);
             println!("population: {:?}", stats);
             assert_eq!(propagate_stats, [0, 0, 9, 0]);
@@ -651,16 +606,18 @@ mod tests {
         let stats_before: Stats;
         let stats_after: Stats;
 
-        stats_before = humans_stats(&population.humans);
+        let humans = Arc::clone(&population.humans);
+        stats_before = humans_stats(&humans);
         let should_be_infected = population.size as i32 * infection_start / 100;
         let tolerance = (should_be_infected as f32 * 0.20) as i32;
         println!("{:?}", stats_before);
         assert!(stats_before.infected <= should_be_infected + tolerance, "{} infected, should be less than {}", stats_before.infected, should_be_infected + tolerance);
         assert!(stats_before.infected >= should_be_infected - tolerance, "{} infected, should be more than {}", stats_before.infected, should_be_infected - tolerance);
 
-        population.propagate();
+        population.propagate_new(THREADS);
 
-        stats_after = humans_stats(&population.humans);
+        let humans = Arc::clone(&population.humans);
+        stats_after = humans_stats(&humans);
         assert_eq!(stats_before.infected, stats_after.infected, "no one should have been infected");
     }
 
@@ -680,7 +637,8 @@ mod tests {
         disease = Disease::new(infection_rate, 0, death_rate, String::from("Test"));
         population = Population::new(start_infected, 0, 0, width, height, disease);
 
-        stats = humans_stats(&population.humans);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("Population after init: {:?}", stats);
 
         // total * proba - 20% < infected < total * proba + 20%
@@ -693,7 +651,7 @@ mod tests {
         let infected_at_start = stats.infected;
         let dead_at_start = stats.dead;
 
-        let propa_stats: [i32; 4] = population.propagate();
+        let propa_stats: [i32; 4] = population.propagate_new(THREADS);
 
         assert!(propa_stats[3] >= dead_at_start);
 
@@ -701,7 +659,8 @@ mod tests {
             assert_eq!(propa_stats[3], 0, "no human should have died");
         }
 
-        stats = humans_stats(&population.humans);
+        let humans = Arc::clone(&population.humans);
+        stats = humans_stats(&humans);
         println!("Population after propagate: {:?}", stats);
 
         assert!(stats.infected <= infected_at_start + width * height * infected_expected);