Store squared limit to reduce operations.

Cargo.lock

@@ -43,6 +43,37 @@ dependencies = [
  "vec_map",
 ]
 
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9dd111b7b7f7d55b72c0a6ae361660ee5853c9af73f70c3c2ef6858b950e2e51"
+dependencies = [
+ "crossbeam-epoch",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5b82ac4a3c2ca9c3460964f020e1402edd5753411d7737aa39c3714ad1b5420e"
+dependencies = [
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d0a5c400df2834b80a4c3327b3aad3a4c4cd4de0629063962b03235697506a28"
+
+[[package]]
+name = "either"
+version = "1.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
+
 [[package]]
 name = "heck"
 version = "0.3.3"
@@ -65,6 +96,7 @@ dependencies = [
 name = "indivisible"
 version = "2.0.0"
 dependencies = [
+ "rayon",
  "structopt",
 ]
 
@@ -76,9 +108,9 @@ checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
 
 [[package]]
 name = "libc"
-version = "0.2.178"
+version = "0.2.182"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "37c93d8daa9d8a012fd8ab92f088405fb202ea0b6ab73ee2482ae66af4f42091"
+checksum = "6800badb6cb2082ffd7b6a67e6125bb39f18782f793520caee8cb8846be06112"
 
 [[package]]
 name = "proc-macro-error"
@@ -106,22 +138,42 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.103"
+version = "1.0.106"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5ee95bc4ef87b8d5ba32e8b7714ccc834865276eab0aed5c9958d00ec45f49e8"
+checksum = "8fd00f0bb2e90d81d1044c2b32617f68fcb9fa3bb7640c23e9c748e53fb30934"
 dependencies = [
  "unicode-ident",
 ]
 
 [[package]]
 name = "quote"
-version = "1.0.42"
+version = "1.0.45"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a338cc41d27e6cc6dce6cefc13a0729dfbb81c262b1f519331575dd80ef3067f"
+checksum = "41f2619966050689382d2b44f664f4bc593e129785a36d6ee376ddf37259b924"
 dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "rayon"
+version = "1.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "368f01d005bf8fd9b1206fb6fa653e6c4a81ceb1466406b81792d87c5677a58f"
+dependencies = [
+ "either",
+ "rayon-core",
+]
+
+[[package]]
+name = "rayon-core"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22e18b0f0062d30d4230b2e85ff77fdfe4326feb054b9783a3460d8435c8ab91"
+dependencies = [
+ "crossbeam-deque",
+ "crossbeam-utils",
+]
+
 [[package]]
 name = "strsim"
 version = "0.8.0"
@@ -174,9 +226,9 @@ dependencies = [
 
 [[package]]
 name = "unicode-ident"
-version = "1.0.22"
+version = "1.0.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9312f7c4f6ff9069b165498234ce8be658059c6728633667c526e27dc2cf1df5"
+checksum = "e6e4313cd5fcd3dad5cafa179702e2b244f760991f45397d14d4ebf38247da75"
 
 [[package]]
 name = "unicode-segmentation"

Cargo.toml

@@ -10,3 +10,4 @@ keywords = [ "primes", "math" ]
 
 [dependencies]
 structopt = "0.3"
+rayon = "1.11"

benchmark.sh

@@ -16,7 +16,7 @@ then
 	exit 1
 fi
 
-while getopts "t:s:" opt
+while getopts "t:s:j:" opt
 do
 	case "$opt" in
 		s)
@@ -26,6 +26,10 @@ do
 		t)
 			TRIALS="$OPTARG"
 			;;
+		j)
+			OPTIONS=("${OPTIONS[@]}" -j "$OPTARG")
+			JOBS=$OPTARG
+			;;
 		*)
 			>&2 echo "Uknown option $opt"
 			exit 1
@@ -36,6 +40,7 @@ done
 echo "Calculating primes up to 1,000,000,000"
 echo "Trials: $TRIALS"
 echo "Sieve segment size: ${SIEVE:-"default"}"
+echo "Number of jobs: ${JOBS:-"default"}"
 TOTAL="0"
 for _ in $(seq "$TRIALS")
 do

src/main.rs

@@ -16,11 +16,16 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+use std::collections::VecDeque;
 use std::fs::File;
 use std::io::{BufRead, BufReader};
 use std::path::PathBuf;
 use std::process;
+use std::sync::{Arc, RwLock};
+use std::sync::mpsc::{Sender, Receiver};
+use std::sync::mpsc;
 use structopt::StructOpt;
+use rayon::ThreadPoolBuilder;
 
 mod worker;
 
@@ -37,13 +42,18 @@ struct Opt {
 	num:usize,
 	#[structopt(short, long, name = "SIZE", default_value = "10485760", help = "Set a custom sieve size")]
 	sieve:usize,
-	//#[structopt(short, long, name = "n", default_value = "1", help = "Number of threads to spawn")]
-	//jobs:u64,
+	#[structopt(short, long, name = "n", default_value = "1", help = "Number of threads to spawn")]
+	jobs:usize,
+}
+
+struct BatchResult {
+	batch_id: u64,
+	primes: Vec<u64>,
 }
 
 fn main() {
 	let opts = Opt::from_args();
-	let mut prime_list = Vec::new();
+	let mut prime_list_raw = Vec::new();
 
 	if opts.import.is_some() {
 		let in_file = File::open(opts.import.unwrap()).unwrap();
@@ -54,7 +64,7 @@ fn main() {
 				break;
 			}
 
-			prime_list.push(prime);
+			prime_list_raw.push(prime);
 		}
 	}
 
@@ -63,31 +73,101 @@ fn main() {
 		process::exit(1);
 	}
 
-	let mut start:usize = if prime_list.is_empty() {
+	let pool = ThreadPoolBuilder::new().num_threads(opts.jobs).build().unwrap();
+	let mut pending_tasks = 0;
+	/* force u64 to avoid overflow if sieve size / opts.num is larger than i32::MAX.
+	 * This is unlikely, but possible.
+	 */
+	let mut batch_num: u64 = 0;
+	let mut last_batch_id: u64 = 0;
+	let mut remaining_batches = VecDeque::<BatchResult>::new();
+	let (tx, rx): (Sender<BatchResult>, Receiver<BatchResult>) = mpsc::channel();
+
+	let mut start:usize = if prime_list_raw.is_empty() {
 		2
 	} else {
-		(*prime_list.last().unwrap() + 1) as usize
+		(*prime_list_raw.last().unwrap() + 1) as usize
 	};
-	while start < opts.num {
-		let end = if start + opts.sieve < opts.num {
-			start + opts.sieve
-		} else {
-			opts.num + 1
-		};
-		let mut new_primes = worker::work_segment(&prime_list, start, end);
+	let mut end = if start + opts.sieve < opts.num {
+		start + opts.sieve
+	} else {
+		opts.num + 1
+	};
+	let mut squared_limit = 0;
 
-		if opts.verbose {
-			for p in &new_primes {
-				println!("{}", *p);
+	let prime_list = Arc::new(RwLock::new(prime_list_raw));
+	loop {
+		if (start < opts.num) && (squared_limit >= (end as u64) ||
+			(prime_list.read().unwrap().is_empty() && pending_tasks == 0))
+		{
+			let prime_list_clone = Arc::clone(&prime_list);
+			let tx_clone = tx.clone();
+			batch_num += 1;
+			let batch_id = batch_num;
+			pool.spawn(move || {
+				let res = worker::work_segment(&prime_list_clone, start, end);
+				tx_clone.send(BatchResult{batch_id, primes: res}).unwrap();
+			});
+			pending_tasks += 1;
+			start += opts.sieve;
+			end = if end + opts.sieve < opts.num {
+				end + opts.sieve
+			} else {
+				opts.num + 1
+			};
+		} else if pending_tasks > 0 {
+			let res = rx.recv().unwrap();
+			pending_tasks -= 1;
+			if res.batch_id != last_batch_id + 1 {
+				if remaining_batches.is_empty() || (res.batch_id > remaining_batches.back().unwrap().batch_id) {
+					remaining_batches.push_back(res);
+				} else if res.batch_id < remaining_batches.front().unwrap().batch_id {
+					remaining_batches.push_front(res);
+				} else {
+					let mut i = 0;
+					while i < remaining_batches.len() {
+						if res.batch_id < remaining_batches[i].batch_id {
+							remaining_batches.insert(i, res);
+							break;
+						}
+						i += 1;
+					}
+				}
+			} else {
+				last_batch_id = res.batch_id;
+
+				if opts.verbose {
+					for p in &res.primes {
+						println!("{}", *p);
+					}
+				}
+				prime_list.write().unwrap().append(&mut res.primes.clone());
+
+				loop {
+					match remaining_batches.pop_front_if(|br| br.batch_id == last_batch_id + 1) {
+						Some(br) => {
+							last_batch_id = br.batch_id;
+							if opts.verbose {
+								for p in &br.primes {
+									println!("{}", *p);
+								}
+							}
+							prime_list.write().unwrap().append(&mut br.primes.clone());
+						},
+						None => break,
+					};
+				}
+
+				squared_limit = prime_list.read().unwrap().last().unwrap().pow(2);
 			}
+		} else {
+			// no more tasks to be added, and all tasks have been processed
+			break;
 		}
-		prime_list.append(&mut new_primes);
-
-		start += opts.sieve;
 	}
 
 	if opts.test {
-		if *prime_list.last().unwrap() == (opts.num as u64) {
+		if *prime_list.read().unwrap().last().unwrap() == (opts.num as u64) {
 			if opts.verbose {
 				println!("{} is prime", opts.num);
 			}
@@ -99,6 +179,6 @@ fn main() {
 			process::exit(1);
 		}
 	} else if !opts.verbose {
-		println!("{}", prime_list.last().unwrap());
+		println!("{}", prime_list.read().unwrap().last().unwrap());
 	}
 }

src/worker.rs

@@ -16,6 +16,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+use std::sync::RwLock;
+
 /**
  * @brief Work on a segment.
  *
@@ -25,13 +27,13 @@
  *
  * @return List of primes found in segment.
  */
-pub fn work_segment(known_primes:&Vec<u64>, start:usize, end:usize) -> Vec<u64> {
+pub fn work_segment(known_primes:&RwLock<Vec<u64>>, start:usize, end:usize) -> Vec<u64> {
 	let mut sieve = vec![true; end - start];
 	let mut found_primes = Vec::new();
 
 	let sqrt_end = (end as f64).sqrt() as usize;
 
-	for p in known_primes {
+	for p in known_primes.read().unwrap().iter() {
 		let prime = *p as usize;
 		if prime > sqrt_end {
 			break;