Improved SIMD MD5 approach

Author: maneatingape

README.md

@@ -1,7 +1,7 @@
 # Advent of Code [![checks-badge]][checks-link] [![docs-badge]][docs-link]
 
 Blazing fast Rust solutions for every [Advent of Code] puzzle from 2015 to 2024, taking
-**501 milliseconds** to solve all 500 stars. Each solution is carefully optimized for performance
+**498 milliseconds** to solve all 500 stars. Each solution is carefully optimized for performance
 while ensuring the code remains concise, readable, and idiomatic.
 
 ## Features
@@ -67,7 +67,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 
 | Year | [2015](#2015) | [2016](#2016) | [2017](#2017) | [2018](#2018) | [2019](#2019) | [2020](#2020) | [2021](#2021) | [2022](#2022) | [2023](#2023) | [2024](#2024) |
 | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
-| Benchmark (ms) | 15 | 111 | 82 | 35 | 15 | 220 | 8 | 6 | 5 | 4 |
+| Benchmark (ms) | 15 | 109 | 82 | 35 | 14 | 220 | 8 | 6 | 5 | 4 |
 
 ## 2024
 
@@ -335,7 +335,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | 2 | [Bathroom Security](https://adventofcode.com/2016/day/2) | [Source](src/year2016/day02.rs) | 29 |
 | 3 | [Squares With Three Sides](https://adventofcode.com/2016/day/3) | [Source](src/year2016/day03.rs) | 24 |
 | 4 | [Security Through Obscurity](https://adventofcode.com/2016/day/4) | [Source](src/year2016/day04.rs) | 79 |
-| 5 | [How About a Nice Game of Chess?](https://adventofcode.com/2016/day/5) | [Source](src/year2016/day05.rs) | 34000 |
+| 5 | [How About a Nice Game of Chess?](https://adventofcode.com/2016/day/5) | [Source](src/year2016/day05.rs) | 33000 |
 | 6 | [Signals and Noise](https://adventofcode.com/2016/day/6) | [Source](src/year2016/day06.rs) | 3 |
 | 7 | [Internet Protocol Version 7](https://adventofcode.com/2016/day/7) | [Source](src/year2016/day07.rs) | 364 |
 | 8 | [Two-Factor Authentication](https://adventofcode.com/2016/day/8) | [Source](src/year2016/day08.rs) | 9 |
@@ -344,7 +344,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | 11 | [Radioisotope Thermoelectric Generators](https://adventofcode.com/2016/day/11) | [Source](src/year2016/day11.rs) | 719 |
 | 12 | [Leonardo's Monorail](https://adventofcode.com/2016/day/12) | [Source](src/year2016/day12.rs) | 1 |
 | 13 | [A Maze of Twisty Little Cubicles](https://adventofcode.com/2016/day/13) | [Source](src/year2016/day13.rs) | 3 |
-| 14 | [One-Time Pad](https://adventofcode.com/2016/day/14) | [Source](src/year2016/day14.rs) | 72000 |
+| 14 | [One-Time Pad](https://adventofcode.com/2016/day/14) | [Source](src/year2016/day14.rs) | 71000 |
 | 15 | [Timing is Everything](https://adventofcode.com/2016/day/15) | [Source](src/year2016/day15.rs) | 1 |
 | 16 | [Dragon Checksum](https://adventofcode.com/2016/day/16) | [Source](src/year2016/day16.rs) | 1 |
 | 17 | [Two Steps Forward](https://adventofcode.com/2016/day/17) | [Source](src/year2016/day17.rs) | 3606 |
@@ -366,7 +366,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | 1 | [Not Quite Lisp](https://adventofcode.com/2015/day/1) | [Source](src/year2015/day01.rs) | 2 |
 | 2 | [I Was Told There Would Be No Math](https://adventofcode.com/2015/day/2) | [Source](src/year2015/day02.rs) | 8 |
 | 3 | [Perfectly Spherical Houses in a Vacuum](https://adventofcode.com/2015/day/3) | [Source](src/year2015/day03.rs) | 95 |
-| 4 | [The Ideal Stocking Stuffer](https://adventofcode.com/2015/day/4) | [Source](src/year2015/day04.rs) | 13000 |
+| 4 | [The Ideal Stocking Stuffer](https://adventofcode.com/2015/day/4) | [Source](src/year2015/day04.rs) | 12000 |
 | 5 | [Doesn't He Have Intern-Elves For This?](https://adventofcode.com/2015/day/5) | [Source](src/year2015/day05.rs) | 38 |
 | 6 | [Probably a Fire Hazard](https://adventofcode.com/2015/day/6) | [Source](src/year2015/day06.rs) | 454 |
 | 7 | [Some Assembly Required](https://adventofcode.com/2015/day/7) | [Source](src/year2015/day07.rs) | 27 |

src/util/md5.rs

@@ -141,10 +141,10 @@ fn common(f: u32, a: u32, b: u32, m: u32, s: u32, k: u32) -> u32 {
 pub mod simd {
     use std::array::from_fn;
     use std::simd::num::SimdUint as _;
-    use std::simd::{LaneCount, Simd, SupportedLaneCount};
+    use std::simd::*;
 
     #[inline]
-    pub fn hash_fixed<const N: usize>(buffers: &mut [[u8; 64]; N], size: usize) -> [[u32; N]; 4]
+    pub fn hash_fixed<const N: usize>(buffers: &mut [[u8; 64]; N], size: usize) -> [Simd<u32, N>; 4]
     where
         LaneCount<N>: SupportedLaneCount,
     {
@@ -245,12 +245,7 @@ pub mod simd {
         c = round4(c, d, a, b, m2, 15, 0x2ad7d2bb);
         b = round4(b, c, d, a, m9, 21, 0xeb86d391);
 
-        [
-            (a0 + a).swap_bytes().to_array(),
-            (b0 + b).swap_bytes().to_array(),
-            (c0 + c).swap_bytes().to_array(),
-            (d0 + d).swap_bytes().to_array(),
-        ]
+        [(a0 + a).swap_bytes(), (b0 + b).swap_bytes(), (c0 + c).swap_bytes(), (d0 + d).swap_bytes()]
     }
 
     #[inline]

src/year2015/day04.rs

@@ -101,8 +101,10 @@ fn worker(shared: &Shared) {
 #[cfg(feature = "simd")]
 mod simd {
     use super::*;
+    use crate::util::bitset::*;
     use crate::util::md5::simd::hash_fixed;
-    use std::simd::{LaneCount, SupportedLaneCount};
+    use std::simd::cmp::SimdPartialEq as _;
+    use std::simd::*;
 
     #[expect(clippy::needless_range_loop)]
     fn check_hash_simd<const N: usize>(
@@ -123,12 +125,13 @@ mod simd {
         }
 
         let [result, ..] = hash_fixed(buffers, size);
+        let bitmask = (result & Simd::splat(0xfffff000)).simd_eq(Simd::splat(0)).to_bitmask();
 
-        for i in 0..N {
+        for i in bitmask.biterator() {
             if result[i] & 0xffffff00 == 0 {
                 shared.second.fetch_min(start + offset + i as u32, Ordering::Relaxed);
                 shared.iter.stop();
-            } else if result[i] & 0xfffff000 == 0 {
+            } else {
                 shared.first.fetch_min(start + offset + i as u32, Ordering::Relaxed);
             }
         }

src/year2016/day05.rs

@@ -111,8 +111,10 @@ fn worker(shared: &Shared) {
 #[cfg(feature = "simd")]
 mod simd {
     use super::*;
+    use crate::util::bitset::*;
     use crate::util::md5::simd::hash_fixed;
-    use std::simd::{LaneCount, SupportedLaneCount};
+    use std::simd::cmp::SimdPartialEq as _;
+    use std::simd::*;
 
     #[expect(clippy::needless_range_loop)]
     fn check_hash_simd<const N: usize>(
@@ -133,11 +135,12 @@ mod simd {
         }
 
         let [result, ..] = hash_fixed(buffers, size);
+        let bitmask = (result & Simd::splat(0xfffff000)).simd_eq(Simd::splat(0)).to_bitmask();
 
-        for i in 0..N {
-            if result[i] & 0xfffff000 == 0 {
-                let mut exclusive = shared.mutex.lock().unwrap();
+        if bitmask != 0 {
+            let mut exclusive = shared.mutex.lock().unwrap();
 
+            for i in bitmask.biterator() {
                 exclusive.found.push((start + offset + i as u32, result[i]));
                 exclusive.mask |= 1 << (result[i] >> 8);