add multithreaded example

examples/multithreaded.rs

@@ -0,0 +1,8 @@
+
+use powlib::{gen::{POWRange, POWChallenge}, solver::POWSolver};
+
+fn main() {
+    let challenge = POWChallenge::make(POWRange::new(0, 20480));
+    let mut solver = POWSolver::new(challenge);
+    println!("Found {} with 8 threads", solver.solve_blocking(8, Some(|x| println!("{x}"))));
+}

src/solver.rs

@@ -1,5 +1,8 @@
-use crate::gen::POWChallenge;
+use std::{sync::{mpsc::{self, Receiver, SyncSender}, Arc, atomic::{AtomicBool, Ordering}}, thread::{self, JoinHandle}};
 
+use crate::{gen::POWChallenge, num::Num};
+
+#[derive(Debug, Clone)]
 pub struct POWSolver {
     challenge: POWChallenge,
     result: Option<u128>
@@ -60,6 +63,68 @@ impl POWSolver {
         return self.chunk_solve(self.challenge.range.min, self.challenge.range.max);
     }
 
+    pub fn chunksize(self: &POWSolver, threads: u8) -> u128 {
+        let range = self.challenge.range.max - self.challenge.range.min;
+        range / threads as u128
+    }
+
+    pub fn solve_blocking(self: &mut POWSolver, threads: u8, callback: Option<fn(u128)>) -> u128 {
+        let (send, recv) = mpsc::sync_channel::<u128>(1);
+        let mut thread_start: u128 = self.challenge.range.min;
+
+        let size = self.chunksize(threads);
+        let mut handles: Vec<JoinHandle<()>> = vec![];
+        let stop = Arc::new(AtomicBool::new(false));
+        let range = self.challenge.range.max - self.challenge.range.min;
+
+        for i in 0..threads {
+            let solver = self.clone();
+            let send = send.clone();
+            let stop = stop.clone();
+
+            let mut end = thread_start + size;
+            if end > range {
+                end -= end % range;
+            }
+
+            handles.push(
+                    thread::spawn(move || {
+                        for j in thread_start..end {
+                            if stop.load(Ordering::Relaxed) { break }
+                            if callback.is_some() {
+                                callback.unwrap()(j);
+                            }
+
+                            if solver.challenge.check(Num::from(j as u128)) {
+                                stop.store(true, Ordering::Relaxed);
+                                send.send(j as u128).unwrap();
+                            }
+                        }
+                    }
+                )
+            );
+
+            thread_start = thread_start + size + 1;
+        }
+
+        let result = recv.recv().unwrap();
+        stop.load(Ordering::Relaxed);
+
+        loop {
+            let mut all_finished = true;
+            for handle in handles.iter() {
+                if !handle.is_finished() {
+                    all_finished = false
+                }
+            }
+            if all_finished { break }
+        }
+
+        self.result = Some(result);
+
+        result
+    }
+
     pub fn new(challenge: POWChallenge) -> POWSolver {
         POWSolver { challenge, result: None }
     }