From c638ecf35d17bba9c7634ea2c4ec4126c61a9705 Mon Sep 17 00:00:00 2001
From: Devin Ragotzy <devin.ragotzy@gmail.com>
Date: Tue, 2 Nov 2021 21:11:37 -0400
Subject: Bring rust benchmarks in line with c benchmarks

---
 benchmarks/rust_hashmap.rs | 135 ++++++++++++++++++++++++++++++---------------
 1 file changed, 91 insertions(+), 44 deletions(-)

diff --git a/benchmarks/rust_hashmap.rs b/benchmarks/rust_hashmap.rs
index d1372e8b..8e9a5250 100644
--- a/benchmarks/rust_hashmap.rs
+++ b/benchmarks/rust_hashmap.rs
@@ -1,44 +1,91 @@
-use std::time::{Instant};
-use std::io::Read;
-
-fn romu_rotl(val: u64, r: u32) -> u64
-    { return (val << r) | (val >> (64 - r)); }
-
-fn romu_trio(s: &mut[u64]) -> u64 {
-    let xp = s[0]; let yp = s[1]; let zp = s[2];
-    s[0] = 15241094284759029579 * zp;
-    s[1] = yp - xp; s[1] = romu_rotl(s[1], 12);
-    s[2] = zp - yp; s[2] = romu_rotl(s[2], 44);
-    return xp;
-}
-
-fn main() {
-    let n = 50_000_000; let mask = (1 << 25) - 1;
-    let mut m = std::collections::HashMap::<u64, u64>::with_capacity(n);
-    let mut rng: [u64; 3] = [1872361123, 123879177, 87739234];
-    println!("Rust HashMap  n = {}, mask = {:#x}", n, mask);
-    let now = Instant::now();
-    for _i in 0..n {
-        let key: u64 = romu_trio(&mut rng) & mask;
-        *m.entry(key).or_insert(0) += 1;
-    }
-    println!("insert  : {}ms  \tsize : {}", now.elapsed().as_millis(), m.len());
-    let now = Instant::now();
-    let mut sum = 0;
-    for i in 0..mask + 1 { if m.contains_key(&i) { sum += 1; }}
-    println!("lookup  : {}ms  \tsum  : {}", now.elapsed().as_millis(), sum);
-
-    let now = Instant::now();
-    let mut sum = 0;
-    for (_, value) in &m { sum += value; }
-    println!("iterate : {}ms  \tsum  : {}", now.elapsed().as_millis(), sum);
-
-    let mut rng: [u64; 3] = [1872361123, 123879177, 87739234];
-    let now = Instant::now();
-    for _ in 0..n {
-        let key: u64 = romu_trio(&mut rng) & mask;
-        m.remove(&key);
-    }
-    println!("remove  : {}ms  \tsize : {}", now.elapsed().as_millis(), m.len());
-    println!("press a key:"); std::io::stdin().bytes().next();
-}
\ No newline at end of file
+use std::{
+    hash::{BuildHasherDefault, Hasher},
+    io::Read,
+    time::Instant,
+};
+
+struct MyHasher {
+    seed: u64,
+}
+
+impl Default for MyHasher {
+    fn default() -> Self {
+        Self { seed: 0xb5ad4eceda1ce2a9_u64 }
+    }
+}
+
+// fn rotl(h: u64, y: u64) -> u64 {
+//     (h << y) | (h >> (64 - y))
+// }
+
+impl Hasher for MyHasher {
+    fn write(&mut self, bytes: &[u8]) {
+        use std::convert::TryInto;
+        self.seed = u64::from_ne_bytes(bytes.try_into().unwrap()).wrapping_mul(0xc6a4a7935bd1e99d);
+    }
+
+    #[inline]
+    fn write_u64(&mut self, i: u64) {
+        self.seed = i.wrapping_mul(0xc6a4a7935bd1e99d);
+    }
+
+    #[inline]
+    fn finish(&self) -> u64 {
+        self.seed
+    }
+}
+
+type MyBuildHasher = BuildHasherDefault<MyHasher>;
+
+#[inline]
+fn romu_rotl(val: u64, r: u32) -> u64 {
+    return (val.wrapping_shl(r)).wrapping_add(val.wrapping_shr(64_u32.wrapping_sub(r)));
+}
+
+fn romu_trio(s: &mut [u64]) -> u64 {
+    let xp = s[0];
+    let yp = s[1];
+    let zp = s[2];
+    s[0] = 15241094284759029579_u64.wrapping_mul(zp);
+    s[1] = yp.wrapping_sub(xp);
+    s[1] = romu_rotl(s[1], 12);
+    s[2] = zp.wrapping_sub(yp);
+    s[2] = romu_rotl(s[2], 44);
+    return xp;
+}
+
+fn main() {
+    let n = 50_000_000;
+    let mask = (1 << 25) - 1;
+
+    let mut m = std::collections::HashMap::<u64, u64, MyBuildHasher>::default();
+    m.reserve(n);
+
+    let mut rng: [u64; 3] = [1872361123, 123879177, 87739234];
+    println!("Rust HashMap  n = {}, mask = {:#x}", n, mask);
+    let now = Instant::now();
+    for _i in 0..n {
+        let key: u64 = romu_trio(&mut rng) & mask;
+        *m.entry(key).or_insert(0) += 1;
+    }
+    println!("insert  : {}ms  \tsize : {}", now.elapsed().as_millis(), m.len());
+    let now = Instant::now();
+    let mut sum = 0;
+    for i in 0..mask + 1 { if m.contains_key(&i) { sum += 1; }}
+    println!("lookup  : {}ms  \tsum  : {}", now.elapsed().as_millis(), sum);
+
+    let now = Instant::now();
+    let mut sum = 0;
+    for (_, value) in &m { sum += value; }
+    println!("iterate : {}ms  \tsum  : {}", now.elapsed().as_millis(), sum);
+
+    let mut rng: [u64; 3] = [1872361123, 123879177, 87739234];
+    let now = Instant::now();
+    for _ in 0..n {
+        let key: u64 = romu_trio(&mut rng) & mask;
+        m.remove(&key);
+    }
+    println!("remove  : {}ms  \tsize : {}", now.elapsed().as_millis(), m.len());
+    println!("press a key:");
+    std::io::stdin().bytes().next();
+}
-- 
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