From 65d470e69aac3acfdf4f7ef238ec49918a810482 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Mon, 12 Oct 2026 15:57:14 +0000
Subject: [PATCH] perf(portfolio): replace .reduce() with for-loop for
 accumulation

Co-authored-by: toreleon <42534763+toreleon@users.noreply.github.com>
---
 .jules/bolt.md         |  4 ++++
 src/tools/portfolio.ts | 21 ++++++++++++---------
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/.jules/bolt.md b/.jules/bolt.md
index 7985023..8eccce3 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -41,3 +41,7 @@
 ## 2024-05-15 - Fast cache keys using integer math
 **Learning:** Calling `new Date().toISOString().slice()` in hot paths (like `cached()` key generation during a backtest loop) adds up significantly (~1ms per thousand calls).
 **Action:** When grouping cache keys by day, use fast integer math `Math.floor(unixSecs / 86400)` instead of string-based date allocations to maintain identical semantics while avoiding object instantiation.
+
+## 2026-10-12 - Replace .reduce() with for-loops to prevent object accumulation overhead
+**Learning:** Using `.reduce()` to accumulate state across an array of objects (like calculating portfolio totals in `src/tools/portfolio.ts`) often involves destructuring or object mutations inside the reducer, which causes unnecessary garbage collection and performance degradation in hot paths.
+**Action:** Replace `.reduce()` operations over arrays with a standard `for` loop and accumulate directly into scalar variables (`let total_a = 0`, etc.), then construct the final object once at the end.
diff --git a/src/tools/portfolio.ts b/src/tools/portfolio.ts
index 406d74a..11839e8 100644
--- a/src/tools/portfolio.ts
+++ b/src/tools/portfolio.ts
@@ -46,15 +46,18 @@ export async function shapeBrokerPortfolio(
     }),
   );
 
-  const totals = positions.reduce(
-    (a, p) => {
-      a.cost_basis_vnd += p.cost_basis_vnd;
-      if (p.market_value_vnd != null) a.market_value_vnd += p.market_value_vnd;
-      if (p.unrealized_pnl_vnd != null) a.unrealized_pnl_vnd += p.unrealized_pnl_vnd;
-      return a;
-    },
-    { cost_basis_vnd: 0, market_value_vnd: 0, unrealized_pnl_vnd: 0 },
-  );
+  let cost_basis_vnd = 0;
+  let market_value_vnd = 0;
+  let unrealized_pnl_vnd = 0;
+
+  for (let i = 0; i < positions.length; i++) {
+    const p = positions[i]!;
+    cost_basis_vnd += p.cost_basis_vnd;
+    if (p.market_value_vnd != null) market_value_vnd += p.market_value_vnd;
+    if (p.unrealized_pnl_vnd != null) unrealized_pnl_vnd += p.unrealized_pnl_vnd;
+  }
+
+  const totals = { cost_basis_vnd, market_value_vnd, unrealized_pnl_vnd };
   const total_equity_vnd = snap.cashVnd + totals.market_value_vnd;
 
   return {