[TASK] Attempted to improve the performance of day11 by executing the iterations in parallel...Unfortunately it just got twice as slow...

Cargo.lock

@@ -5,6 +5,7 @@ name = "advent-of-code-2020-rust"
 version = "0.1.0"
 dependencies = [
  "lazy_static",
+ "rayon",
  "regex",
  "usize_cast",
 ]
@@ -18,18 +19,147 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "autocfg"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "const_fn"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cd51eab21ab4fd6a3bf889e2d0958c0a6e3a61ad04260325e919e652a2a62826"
+
+[[package]]
+name = "crossbeam-channel"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dca26ee1f8d361640700bde38b2c37d8c22b3ce2d360e1fc1c74ea4b0aa7d775"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "94af6efb46fef72616855b036a624cf27ba656ffc9be1b9a3c931cfc7749a9a9"
+dependencies = [
+ "cfg-if",
+ "crossbeam-epoch",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1aaa739f95311c2c7887a76863f500026092fb1dce0161dab577e559ef3569d"
+dependencies = [
+ "cfg-if",
+ "const_fn",
+ "crossbeam-utils",
+ "lazy_static",
+ "memoffset",
+ "scopeguard",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "02d96d1e189ef58269ebe5b97953da3274d83a93af647c2ddd6f9dab28cedb8d"
+dependencies = [
+ "autocfg",
+ "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 = "hermit-abi"
+version = "0.1.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5aca5565f760fb5b220e499d72710ed156fdb74e631659e99377d9ebfbd13ae8"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "lazy_static"
 version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
+[[package]]
+name = "libc"
+version = "0.2.81"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1482821306169ec4d07f6aca392a4681f66c75c9918aa49641a2595db64053cb"
+
 [[package]]
 name = "memchr"
 version = "2.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0ee1c47aaa256ecabcaea351eae4a9b01ef39ed810004e298d2511ed284b1525"
 
+[[package]]
+name = "memoffset"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "157b4208e3059a8f9e78d559edc658e13df41410cb3ae03979c83130067fdd87"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "num_cpus"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "05499f3756671c15885fee9034446956fff3f243d6077b91e5767df161f766b3"
+dependencies = [
+ "hermit-abi",
+ "libc",
+]
+
+[[package]]
+name = "rayon"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b0d8e0819fadc20c74ea8373106ead0600e3a67ef1fe8da56e39b9ae7275674"
+dependencies = [
+ "autocfg",
+ "crossbeam-deque",
+ "either",
+ "rayon-core",
+]
+
+[[package]]
+name = "rayon-core"
+version = "1.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ab346ac5921dc62ffa9f89b7a773907511cdfa5490c572ae9be1be33e8afa4a"
+dependencies = [
+ "crossbeam-channel",
+ "crossbeam-deque",
+ "crossbeam-utils",
+ "lazy_static",
+ "num_cpus",
+]
+
 [[package]]
 name = "regex"
 version = "1.4.2"
@@ -48,6 +178,12 @@ version = "0.6.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3b181ba2dcf07aaccad5448e8ead58db5b742cf85dfe035e2227f137a539a189"
 
+[[package]]
+name = "scopeguard"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
+
 [[package]]
 name = "thread_local"
 version = "1.0.1"

Cargo.toml

@@ -9,4 +9,5 @@ edition = "2018"
 [dependencies]
 regex = "1"
 lazy_static = "1.4.0"
-usize_cast = "1.0.0"
+usize_cast = "1.0.0"
+rayon = "1.5.0"

src/day11.rs

@@ -2,19 +2,27 @@ use super::util;
 use crate::day11::GridState::Floor;
 use crate::day11::GridState::FilledSeat;
 use crate::day11::GridState::EmptySeat;
+use rayon::prelude::*;
+use std::time::Instant;
 
 pub fn solve() {
     let lines = util::read_file("input/day11.txt");
 
     let seats = Seats::parse(&lines);
 
+    let now = Instant::now();
+
     let part1 = solve_part1(&seats);
 
+    println!("Part 1 took: {} μs", now.elapsed().as_micros());
     println!("Day 11 Part 1: {}", part1);
 
+    let now2 = Instant::now();
+
     let visible_chairs = seats.calculate_all_visible_chairs();
     let part2 = solve_part2(&seats, &visible_chairs);
 
+    println!("Part 2 took: {} μs", now2.elapsed().as_micros());
     println!("Day 11 Part 2: {}", part2);
 }
 
@@ -23,28 +31,39 @@ fn solve_part1(seats: &Seats) -> usize {
     let mut last_seats = seats.clone();
     let mut next_seats = seats.clone();
 
-    loop {
-        let mut changes = false;
-        for y in 0..seats.height {
-            for x in 0..seats.width {
-                let seat = last_seats.get(&x, &y);
-                if seat != &Floor {
-                    let occupied = last_seats.count_occupied_neighbors(&x, &y);
-                    if seat == &EmptySeat && occupied == 0 {
-                        changes = true;
-                        next_seats.set(&x, &y, FilledSeat);
-                    } else if seat == &FilledSeat && occupied >= 4 {
-                        next_seats.set(&x, &y, EmptySeat);
-                        changes = true;
-                    }
-                }
+    let mut seat_idxs = Vec::new();
+    for y in 0..seats.height {
+        for x in 0..seats.width {
+            let seat = seats.get(&x, &y);
+            if seat != &Floor {
+                seat_idxs.push((x, y));
             }
         }
-        // next_seats.print();
-        if !changes {
+    }
+    loop {
+        let changes: Vec<(usize, usize, &GridState)> = seat_idxs.par_iter().map(|pos| {
+            let x = &pos.0;
+            let y = &pos.1;
+            let seat = last_seats.get(x, y);
+            let occupied = last_seats.count_occupied_neighbors(x, y);
+            if seat == &EmptySeat && occupied == 0 {
+                return Option::from((pos.0, pos.1, &FilledSeat));
+            } else if seat == &FilledSeat && occupied >= 4 {
+                return Option::from((pos.0, pos.1, &EmptySeat));
+            } else {
+                return Option::None;
+            }
+        }).filter(|o| o.is_some()).map(|o| o.unwrap()).collect::<Vec<_>>();
+
+        if changes.is_empty() {
             break;
         }
 
+        for change in changes {
+            next_seats.set(&change.0, &change.1, *change.2);
+        }
+        // next_seats.print();
+
         last_seats = next_seats.clone();
     }
     return last_seats.grid.iter().filter(|s| s == &&FilledSeat).count();
@@ -55,7 +74,11 @@ fn solve_part2(seats: &Seats, visible_chairs: &Vec<Option<Vec<(usize, usize)>>>)
     let mut last_seats = seats.clone();
     let mut next_seats = seats.clone();
 
+    let mut calc_times = Vec::new();
+    let mut copy_times = Vec::new();
+
     loop {
+        let calc_start = Instant::now();
         let mut changes = false;
         for y in 0..seats.height {
             for x in 0..seats.width {
@@ -76,9 +99,15 @@ fn solve_part2(seats: &Seats, visible_chairs: &Vec<Option<Vec<(usize, usize)>>>)
         if !changes {
             break;
         }
+        calc_times.push(calc_start.elapsed().as_micros());
 
+        let now = Instant::now();
         last_seats = next_seats.clone();
+        copy_times.push(now.elapsed().as_micros());
     }
+
+    println!("Avg calc time: {} μs", calc_times.iter().sum::<u128>() / (calc_times.len() as u128));
+    println!("Avg copy time: {} μs", copy_times.iter().sum::<u128>() / (copy_times.len() as u128));
     return last_seats.grid.iter().filter(|s| s == &&FilledSeat).count();
 }