Forgot to add one to pp in parallel implementation.

In English we say "composite" for numbers which are composed as opposed
to prime.

Cargo.lock

@@ -1,5 +1,7 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+version = 3
+
 [[package]]
 name = "ansi_term"
 version = "0.11.0"
@@ -20,12 +22,24 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "autocfg"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
+
 [[package]]
 name = "bitflags"
 version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
 
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
 [[package]]
 name = "clap"
 version = "2.33.3"
@@ -41,6 +55,56 @@ dependencies = [
  "vec_map",
 ]
 
+[[package]]
+name = "crossbeam-channel"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e54ea8bc3fb1ee042f5aace6e3c6e025d3874866da222930f70ce62aceba0bfa"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6455c0ca19f0d2fbf751b908d5c55c1f5cbc65e03c4225427254b46890bdde1e"
+dependencies = [
+ "cfg-if",
+ "crossbeam-epoch",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c00d6d2ea26e8b151d99093005cb442fb9a37aeaca582a03ec70946f49ab5ed9"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+ "lazy_static",
+ "memoffset",
+ "scopeguard",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b5e5bed1f1c269533fa816a0a5492b3545209a205ca1a54842be180eb63a16a6"
+dependencies = [
+ "cfg-if",
+ "lazy_static",
+]
+
+[[package]]
+name = "either"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
+
 [[package]]
 name = "heck"
 version = "0.3.2"
@@ -63,6 +127,7 @@ dependencies = [
 name = "indivisible"
 version = "2.0.0"
 dependencies = [
+ "rayon",
  "structopt",
 ]
 
@@ -78,6 +143,25 @@ version = "0.2.87"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "265d751d31d6780a3f956bb5b8022feba2d94eeee5a84ba64f4212eedca42213"
 
+[[package]]
+name = "memoffset"
+version = "0.6.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5aa361d4faea93603064a027415f07bd8e1d5c88c9fbf68bf56a285428fd79ce"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "num_cpus"
+version = "1.13.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "19e64526ebdee182341572e50e9ad03965aa510cd94427a4549448f285e957a1"
+dependencies = [
+ "hermit-abi",
+ "libc",
+]
+
 [[package]]
 name = "proc-macro-error"
 version = "1.0.4"
@@ -120,6 +204,37 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "rayon"
+version = "1.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c06aca804d41dbc8ba42dfd964f0d01334eceb64314b9ecf7c5fad5188a06d90"
+dependencies = [
+ "autocfg",
+ "crossbeam-deque",
+ "either",
+ "rayon-core",
+]
+
+[[package]]
+name = "rayon-core"
+version = "1.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d78120e2c850279833f1dd3582f730c4ab53ed95aeaaaa862a2a5c71b1656d8e"
+dependencies = [
+ "crossbeam-channel",
+ "crossbeam-deque",
+ "crossbeam-utils",
+ "lazy_static",
+ "num_cpus",
+]
+
+[[package]]
+name = "scopeguard"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
+
 [[package]]
 name = "strsim"
 version = "0.8.0"

Cargo.toml

@@ -12,3 +12,4 @@ keywords = ["primes", "math"]
 
 [dependencies]
 structopt = "0.3.13"
+rayon = "1.5"

README.md

@@ -1,10 +1,9 @@
-===================
-*** Indivisible ***
-===================
+# Indivisible
+
 Indivisible is an optimized prime number generator and tester written in Rust.
 
-# Build & Installation
-----------------------
+## Build & Installation
+
 To build the project you will require the Rust compiler and build
 system, `cargo`. At which point you simply run `cargo build` in the root
 directory of the project. To create an optimized release build append
@@ -15,8 +14,8 @@ the manpage documentation by running the `install` script. In a similar
 manner, you can run the `uninstall` script to remove the previously
 installed binary and documentation.
 
-# Usage
--------
+## Usage
+
 The purpose of Indivisible is to find the nth prime and all the primes
 before it. The basic usage is `indivisible <n>` where `n` is the ordinal
 of the prime you'd like to find. To display all primes before `n`, you
@@ -27,22 +26,23 @@ can also import prime numbers previously computed with the `--import` or
 `-i` option. To store already computed primes you are expected to use
 piping like any UNIX user would expect. Here is an example:
 
+```bash
 # store first 100 primes in ./primes
 indivisible -v 100 > ./primes
 # appends next 400 primes
 indivisible -i ./primes -v 500 >> ./primes
 # display the 600th prime
 indivisible -i ./primes 600
+```
 
-# Legacy
---------
-This project was originally written in C. It can be found on my GitLab
-page.[1]
+## Legacy
+
+This project was originally written in C. It can be found in the
+[indivisible-legacy repository](https://gitlab.com/naortega/Indivisible-legacy)
+on my GitLab.
+
+## License
 
-# License
----------
 This project is licensed under the terms & conditions of the GNU General
 Public License version 3 or greater (see `LICENSE` file for more
 information).
-
-[1] https://gitlab.com/naortega/Indivisible-legacy

src/main.rs

@@ -35,7 +35,7 @@ struct Opt
 	#[structopt(short, long, help = "Test if n is prime instead of generation")]
 	test:bool,
 	#[structopt(help = "Ordinal of the prime to generate")]
-	n:usize,
+	n:u64,
 }
 
 fn main()
@@ -50,12 +50,9 @@ fn main()
 	{
 		let in_file = File::open(opts.import.unwrap()).unwrap();
 		let reader = BufReader::new(in_file);
-		for line in reader.lines()
-		{
-			let line = line.unwrap();
-			let aux:u64 = line.parse().unwrap();
-			primes.push_back(aux);
-		}
+		reader.lines().into_iter().for_each(|x| {
+			primes.push_back(x.unwrap().parse().unwrap());
+		});
 	}
 
 	if opts.test
@@ -64,17 +61,17 @@ fn main()
 		// if no primes were imported, test from beginning (2)
 		if primes.len() == 0
 		{
-			res = test::is_prime(n as u64);
+			res = test::is_prime(n);
 		}
 		// `n` should be in `primes` if the last prime is larger than `n`
-		else if primes.back().unwrap() >= &(n as u64)
+		else if primes.back().unwrap() >= &(n)
 		{
-			res = primes.contains(&(n as u64));
+			res = primes.contains(&(n));
 		}
 		// we can memory test `n` if the last prime is >= sqrt(n)
 		else if primes.back().unwrap() >= &((n as f64).sqrt() as u64)
 		{
-			res = test::is_prime_mem(n as u64, &primes)
+			res = test::is_prime_mem(n, &primes)
 		}
 		/*
 		 * if we have less primes than sqrt(n) then we can test all those
@@ -83,10 +80,10 @@ fn main()
 		 */
 		else
 		{
-			res = test::is_prime_mem(n as u64, &primes);
+			res = test::is_prime_mem(n, &primes);
 			if res
 			{
-				res = test::is_prime_f(n as u64, primes.back().unwrap() + 2);
+				res = test::is_prime_f(n, primes.back().unwrap() + 2);
 			}
 		}
 
@@ -110,9 +107,9 @@ fn main()
 	else
 	{
 		// if `primes` already contains the nth prime, print it
-		if primes.len() >= n
+		if primes.len() >= n as usize
 		{
-			println!("{}", primes.get(n-1).unwrap());
+			println!("{}", primes.get((n as usize) - 1).unwrap());
 		}
 		else
 		{
@@ -137,7 +134,7 @@ fn main()
 				candidate = *primes.back().unwrap() + 2;
 			}
 
-			while primes.len() < n
+			while primes.len() < n as usize
 			{
 				if test::is_prime_mem(candidate, &primes)
 				{
@@ -153,7 +150,7 @@ fn main()
 
 			if !opts.verbose
 			{
-				println!("{}", primes.get(n-1).unwrap());
+				println!("{}", primes.get((n as usize) - 1).unwrap());
 			}
 		}
 	}

src/test.rs

@@ -17,12 +17,18 @@
  */
 
 use std::collections::VecDeque;
+use rayon::prelude::*;
 
 pub fn is_prime_f(n:u64, b:u64) -> bool
 {
 	assert_ne!(b, 0);
 	assert_ne!(b, 1);
 
+	if n == 1
+	{
+		return false;
+	}
+
 	let mut start = b;
 	if start == 2
 	{
@@ -42,14 +48,9 @@ pub fn is_prime_f(n:u64, b:u64) -> bool
 	}
 
 	let limit = (n as f64).sqrt() as u64 + 1;
-	for i in (start..limit).step_by(2)
-	{
-		if n % i == 0
-		{
-			return false;
-		}
-	}
-	return true;
+	let composite = (start..limit).step_by(2).collect::<Vec<u64>>()
+		.par_iter().any(|x| n % x == 0);
+	return !composite;
 }
 
 pub fn is_prime(n:u64) -> bool
@@ -60,12 +61,8 @@ pub fn is_prime(n:u64) -> bool
 pub fn is_prime_mem(n:u64, primes:&VecDeque<u64>) -> bool
 {
 	let limit = (n as f64).sqrt() as u64;
-	for i in primes.iter().take_while(|x| **x <= limit)
-	{
-		if n % *i == 0
-		{
-			return false;
-		}
-	}
-	return true;
+	let pp = primes.partition_point(|x| *x < limit);
+	//let composite = primes.par_iter().take(pp+1).any(|x| n % *x == 0);
+	let composite = primes.iter().take(pp+1).any(|x| n % *x == 0);
+	return !composite;
 }