From 57a4e799a895935b0fbb5eea8653e43eefd49975 Mon Sep 17 00:00:00 2001
From: Seth Etter <sethetter@gmail.com>
Date: Tue, 5 Dec 2023 22:03:57 -0600
Subject: [PATCH] use workers!

---
 2023/day05/part2-worker.ts | 38 +++++++++++++++++++++++++++++++++
 2023/day05/part2.ts        | 43 ++++++++++++++++++++++++++------------
 2 files changed, 68 insertions(+), 13 deletions(-)
 create mode 100644 2023/day05/part2-worker.ts

diff --git a/2023/day05/part2-worker.ts b/2023/day05/part2-worker.ts
new file mode 100644
index 0000000..0c6e6da
--- /dev/null
+++ b/2023/day05/part2-worker.ts
@@ -0,0 +1,38 @@
+import { assert } from "https://deno.land/std@0.208.0/assert/mod.ts";
+import { MapRanges } from "./part2.ts";
+
+type MessageData = {
+  range: [number, number];
+  mapRanges: MapRanges[];
+};
+
+self.onmessage = ({ data: { range, mapRanges } }: { data: MessageData }) => {
+  const [from, to] = range;
+  console.log(`(start) worker ${from}-${to}`);
+  let minLocNum = Infinity;
+  for (let j = 0; j < to - from; j++) {
+    const seed = from + j;
+    const locNum = getLocationNumber(seed, mapRanges);
+    if (locNum < minLocNum) minLocNum = locNum;
+  }
+  self.postMessage({ minLocNum });
+  console.log(`(end) worker ${from}-${to}: ${minLocNum}`);
+  self.close();
+};
+
+function getLocationNumber(seed: number, mapRanges: MapRanges[]): number {
+  let current = "seed";
+  let currentNum = seed;
+  while (current !== "location") {
+    const mapRange = mapRanges.find(({ from }) => from === current);
+    assert(mapRange, `mapRange not found for: ${current}`);
+
+    const range = mapRange.ranges.find(
+      (r) => currentNum >= r.fromStart && currentNum <= r.fromStart + r.range,
+    );
+    if (range) currentNum = currentNum + (range.toStart - range.fromStart);
+
+    current = mapRange.to;
+  }
+  return currentNum;
+}
diff --git a/2023/day05/part2.ts b/2023/day05/part2.ts
index 1975b49..2818e45 100644
--- a/2023/day05/part2.ts
+++ b/2023/day05/part2.ts
@@ -9,13 +9,13 @@ if (import.meta.main) {
   console.log(await answer(input));
 }
 
-type Range = {
+export type Range = {
   fromStart: number;
   toStart: number;
   range: number;
 };
 
-type MapRanges = {
+export type MapRanges = {
   from: string;
   to: string;
   ranges: Range[];
@@ -50,17 +50,24 @@ export async function answer(input: string): Promise<number> {
     const to = from + seedRangeLines[i + 1];
     seedRanges.push([from, to]);
   }
-  const rangeMins = await Promise.all(
-    seedRanges.map(
-      ([from, to]) =>
-        new Promise<number>((resolve) => {
-          let minLocNum = Infinity;
-          for (let j = 0; j < to - from; j++) {
-            const seed = from + j;
-            const locNum = getLocationNumber(seed, mapRanges);
-            if (locNum < minLocNum) minLocNum = locNum;
-          }
-          return resolve(minLocNum);
+
+  const rangeMins: number[] = await Promise.all(
+    splitRanges(seedRanges).map(
+      (range) =>
+        new Promise((resolve, reject) => {
+          const worker = new Worker(
+            new URL("./part2-worker.ts", import.meta.url).href,
+            {
+              type: "module",
+            },
+          );
+          worker.postMessage({ range, mapRanges });
+          worker.onmessage = ({ data }) => {
+            if (typeof data?.minLocNum !== "number") {
+              return reject(new Error(`invalid message: ${data}`));
+            }
+            return resolve(data.minLocNum);
+          };
         }),
     ),
   );
@@ -68,6 +75,16 @@ export async function answer(input: string): Promise<number> {
   return Math.min(...rangeMins);
 }
 
+function splitRanges(ranges: [number, number][]): [number, number][] {
+  const newRanges: [number, number][] = [];
+  for (const [from, to] of ranges) {
+    const middle = Math.ceil(from + (to - from) / 2);
+    newRanges.push([from, middle]);
+    newRanges.push([middle + 1, to]);
+  }
+  return newRanges;
+}
+
 function getLocationNumber(seed: number, mapRanges: MapRanges[]): number {
   let current = "seed";
   let currentNum = seed;
-- 
2.51.2