From fef110e48d0a487abf4d5c5ce07a9b7ad1087aaf Mon Sep 17 00:00:00 2001
From: seonghobae <8172694+seonghobae@users.noreply.github.com>
Date: Mon, 24 Aug 2026 14:01:23 +0000
Subject: [PATCH] perf: optimize computeTaskMetrics with TypedArray and
 standard loops

Replaces Array.prototype.reduce and forEach with standard for loops
and substitutes the Map cache with an Int32Array in computeTaskMetrics
to eliminate JS engine callback allocation, garbage collection, and
hash-lookup overhead in hot loops.
---
 .jules/bolt.md |  3 +++
 app.js         | 24 +++++++++++++++---------
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/.jules/bolt.md b/.jules/bolt.md
index b08b203a..66beb5eb 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -4,3 +4,6 @@
 ## 2026-07-12 - Optimize renderTaskRow DOM allocations
 **Learning:** Caching unattached template nodes and instantiating them via `.cloneNode(false)` reduces DOM instantiation overhead in O(N) render loops significantly.
 **Action:** Apply this optimization to other hot-path rendering elements such as rows, cells, and stack containers.
+## 2026-08-24 - Optimize computeTaskMetrics with Int32Array and standard loops
+**Learning:** In hot loops over large array of tasks, using standard `for` loops and contiguous typed arrays (e.g., `Int32Array`) rather than standard `Map` caching and `Array.prototype.reduce`/`forEach` eliminates the overhead of JS engine callback allocation, garbage collection, and hash-lookups.
+**Action:** Replace `Map` usages paired with functional iteration loops with standard indexed loops and TypedArrays for primitive data mappings whenever processing metrics for performance-critical high-iteration loops.
diff --git a/app.js b/app.js
index a04aae71..a9dc136a 100644
--- a/app.js
+++ b/app.js
@@ -1370,21 +1370,27 @@ function validateDateRange(startLabel, startValue, endLabel, endValue, errors) {
 }
 
 function computeTaskMetrics() {
-  // ⚡ Bolt: Cache durationDays during total calculation to avoid recalculating for every task
-  const durationCache = new Map();
-  const totalDays = state.tasks.reduce((sum, task) => {
+  // ⚡ Bolt: Use Int32Array instead of Map for O(1) contiguous memory access without hash overhead
+  // ⚡ Bolt: Replace reduce/forEach with standard for loops to eliminate JS engine callback allocation
+  const len = state.tasks.length;
+  const durationCache = new Int32Array(len);
+  let totalDays = 0;
+
+  for (let i = 0; i < len; i++) {
+    const task = state.tasks[i];
     const duration = calculateDurationDays(task.plannedStartDate, task.plannedEndDate);
-    durationCache.set(task.id, duration);
-    return sum + duration;
-  }, 0);
+    durationCache[i] = duration;
+    totalDays += duration;
+  }
 
   const baseDate = state.baseDate;
   const byTask = new Map();
   let totalWeightedPlannedRatio = 0;
   let totalWeightedActualRatio = 0;
 
-  state.tasks.forEach((task) => {
-    const durationDays = durationCache.get(task.id);
+  for (let i = 0; i < len; i++) {
+    const task = state.tasks[i];
+    const durationDays = durationCache[i];
     const weightRatio = totalDays > 0 ? durationDays / totalDays : 0;
     const plannedProgressRatio = calculatePlannedProgressRatio(baseDate, task.plannedStartDate, task.plannedEndDate, durationDays);
     const actualProgressRatio = (ACTUAL_PROGRESS_MAP[task.actualProgressStatus] || 0) / 100;
@@ -1408,7 +1414,7 @@ function computeTaskMetrics() {
       plannedDateWarning,
       actualDateWarning
     });
-  });
+  }
 
   return {
     totalDays,