From e61d8861ce4161501d1a915674e7dd4e7ad597e1 Mon Sep 17 00:00:00 2001
From: Anson Biggs <anson@ansonbiggs.com>
Date: Thu, 31 Mar 2022 11:02:52 -0700
Subject: [PATCH] updated code borrowed from internet

---
 .gitignore       |   3 +
 rust/Cargo.toml  |  13 ++++
 rust/src/main.rs | 156 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 172 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 rust/Cargo.toml
 create mode 100644 rust/src/main.rs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..2280feb
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+target/
+debug/
+rust/Cargo.lock
\ No newline at end of file
diff --git a/rust/Cargo.toml b/rust/Cargo.toml
new file mode 100644
index 0000000..37355f6
--- /dev/null
+++ b/rust/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+name = "rust"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rayon = "1.5.1"
+rand = "0.8.5"
+
+[dev-dependencies]
+quickcheck = "0.8.0"
\ No newline at end of file
diff --git a/rust/src/main.rs b/rust/src/main.rs
new file mode 100644
index 0000000..6eafc20
--- /dev/null
+++ b/rust/src/main.rs
@@ -0,0 +1,156 @@
+use rayon::join;
+
+fn partition<T, F>(d: &mut [T], is_less: &F) -> usize
+where
+    F: Fn(&T, &T) -> bool,
+{
+    d.swap(0, d.len() / 2);
+    let mut mid = 0;
+    for i in 1..d.len() {
+        if is_less(&d[i], &d[0]) {
+            mid += 1;
+            d.swap(i, mid);
+        }
+    }
+    d.swap(0, mid);
+    mid
+}
+
+fn insert_sort<T, F>(d: &mut [T], is_less: &F)
+where
+    F: Fn(&T, &T) -> bool,
+{
+    for i in 1..d.len() {
+        let mut n = i;
+        while n > 0 && is_less(&d[n], &d[n - 1]) {
+            d.swap(n, n - 1);
+            n -= 1;
+        }
+    }
+}
+
+fn quick_sort<T, F>(d: &mut [T], is_less: &F)
+where
+    F: Fn(&T, &T) -> bool,
+{
+    if d.len() > 30 {
+        let mut mid = partition(d, is_less);
+        if mid < d.len() / 2 {
+            mid += 1;
+        }
+        let (left, right) = d.split_at_mut(mid);
+        quick_sort(left, is_less);
+        quick_sort(right, is_less);
+    } else {
+        insert_sort(d, is_less);
+    }
+}
+
+fn par_quick_sort<T, F>(d: &mut [T], is_less: &F)
+where
+    F: Fn(&T, &T) -> bool + Send + Sync,
+    T: Send,
+{
+    if d.len() > 30 {
+        let mut mid = partition(d, is_less);
+        if mid < d.len() / 2 {
+            mid += 1;
+        }
+        let (left, right) = d.split_at_mut(mid);
+
+        if right.len() > 100_000 {
+            join(
+                || par_quick_sort(left, is_less),
+                || par_quick_sort(right, is_less),
+            );
+        } else {
+            quick_sort(left, is_less);
+            quick_sort(right, is_less);
+        }
+    } else {
+        insert_sort(d, is_less);
+    }
+}
+
+pub trait QSort<T> {
+    fn qsort(&mut self);
+
+    fn is_sorted(&self) -> bool;
+}
+
+impl<T> QSort<T> for [T]
+where
+    T: Ord,
+{
+    fn qsort(&mut self) {
+        quick_sort(self, &|a: &T, b: &T| a.lt(b));
+    }
+
+    fn is_sorted(&self) -> bool {
+        self.windows(2).all(|w| w[0] <= w[1])
+    }
+}
+
+pub trait ParQSort<T> {
+    fn par_qsort(&mut self);
+}
+
+impl<T> ParQSort<T> for [T]
+where
+    T: Ord + Send,
+{
+    fn par_qsort(&mut self) {
+        par_quick_sort(self, &|a: &T, b: &T| a.lt(b));
+    }
+}
+
+use rand::distributions::{Distribution, Uniform};
+use rand::thread_rng;
+use rayon::prelude::*;
+use std::time::Instant;
+
+fn main() {
+    let len = 50_000_000;
+    let orig: Vec<i32> = Uniform::from(0..1_000_000_000)
+        .sample_iter(&mut thread_rng())
+        .take(len)
+        .collect();
+
+    macro_rules! test_sort {
+        ($name:expr, $sort:ident) => {
+            println!(
+                "Sorting {} million numbers with {} in Rust ...",
+                len / 1_000_000,
+                $name
+            );
+            let mut data = orig.clone();
+            let start = Instant::now();
+            data.$sort();
+            println!("Time: {:.2?}", start.elapsed());
+            assert!(data.is_sorted());
+        }
+    }
+
+    test_sort!("naive quicksort", qsort);
+    test_sort!("stdlib quicksort", sort_unstable);
+    test_sort!("naive parallel quicksort", par_qsort);
+    test_sort!("Rayon quicksort", par_sort_unstable);
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use quickcheck::quickcheck;
+
+    quickcheck! {
+        fn test_all(d: Vec<i32>) -> bool {
+            let mut d = d;
+
+            let mut expected = d.clone();
+            expected.sort_unstable();
+            d.par_qsort();
+
+            expected == d
+        }
+    }
+}
\ No newline at end of file