⚡ Bolt: Replace .reduce() with for loops to optimize allocations and iteration

.jules/bolt.md

@@ -41,3 +41,6 @@
 ## 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.
+## 2025-01-01 - Consolidating Array Operations
+**Learning:** Replacing chained `.reduce()` calls that iterate over the same array multiple times with a single `for` loop reduces iterations from O(N*K) to O(N). Additionally, avoiding object allocations inside hot loops (like in `statsFromRecords`) prevents unnecessary garbage collection overhead.
+**Action:** When extracting multiple aggregates from a single array in a hot path, always favor a single `for` loop over chaining multiple `.reduce()` or `.map()` passes.

src/agent/backtestRunner.ts

@@ -147,10 +147,13 @@ async function markToMarket(
   priceAt: (ticker: string) => number | null,
 ): Promise<number> {
   const snap = await broker.snapshot();
-  return snap.positions.reduce(
-    (sum, p) => sum + positionValue(p, priceAt(p.ticker)),
-    snap.cashVnd,
-  );
+  // ⚡ Bolt: Replaced .reduce() with standard loop to avoid function allocation in hot path
+  let sum = snap.cashVnd;
+  for (let i = 0; i < snap.positions.length; i++) {
+    const p = snap.positions[i]!;
+    sum += positionValue(p, priceAt(p.ticker));
+  }
+  return sum;
 }
 
 async function recordGuardrailReject(
@@ -464,14 +467,25 @@ export async function runBacktestSession(
   const finalBench = last?.benchmark_mtm_vnd ?? opts.initialCash;
   const totalReturn = (finalMtm / opts.initialCash - 1) * 100;
   const benchReturn = (finalBench / opts.initialCash - 1) * 100;
+  // ⚡ Bolt: Consolidated multiple .reduce() passes into single loops for O(n) instead of O(n*k) performance
+
   let runningPeak = opts.initialCash;
-  const maxDD = equityRows.reduce((mn, r) => {
+  let maxDD = 0;
+  for (let i = 0; i < equityRows.length; i++) {
+    const r = equityRows[i]!;
     runningPeak = Math.max(runningPeak, r.mtm_vnd);
-    return Math.min(mn, r.mtm_vnd / runningPeak - 1);
-  }, 0);
-  const totalCost = turnRows.reduce((s, r) => s + (r.cost_usd ?? 0), 0);
-  const totalIn = turnRows.reduce((s, r) => s + (r.in_tokens ?? 0), 0);
-  const totalOut = turnRows.reduce((s, r) => s + (r.out_tokens ?? 0), 0);
+    maxDD = Math.min(maxDD, r.mtm_vnd / runningPeak - 1);
+  }
+
+  let totalCost = 0;
+  let totalIn = 0;
+  let totalOut = 0;
+  for (let i = 0; i < turnRows.length; i++) {
+    const r = turnRows[i]!;
+    totalCost += r.cost_usd ?? 0;
+    totalIn += r.in_tokens ?? 0;
+    totalOut += r.out_tokens ?? 0;
+  }
 
   const summary: SummaryPayload = {
     runId,

src/tui/hooks/useAgentStream.ts

@@ -97,15 +97,22 @@ function blocksFromRecords(records: SessionRecord[]): ChatBlock[] {
 }
 
 function statsFromRecords(records: SessionRecord[]): TurnStats {
-  return records.reduce<TurnStats>((acc, r) => {
-    if (r.type !== "result") return acc;
-    return {
-      inTokens: acc.inTokens + (r.usage?.inputTokens ?? 0),
-      outTokens: acc.outTokens + (r.usage?.outputTokens ?? 0),
-      costUsd: acc.costUsd + (r.costUsd ?? 0),
-      sessionId: r.sdkSessionId ?? acc.sessionId,
-    };
-  }, { inTokens: 0, outTokens: 0, costUsd: 0 });
+  // ⚡ Bolt: Replaced .reduce() with standard loop to avoid object allocation and GC overhead per record
+  let inTokens = 0;
+  let outTokens = 0;
+  let costUsd = 0;
+  let sessionId: string | undefined;
+
+  for (let i = 0; i < records.length; i++) {
+    const r = records[i]!;
+    if (r.type !== "result") continue;
+    inTokens += r.usage?.inputTokens ?? 0;
+    outTokens += r.usage?.outputTokens ?? 0;
+    costUsd += r.costUsd ?? 0;
+    if (r.sdkSessionId) sessionId = r.sdkSessionId;
+  }
+
+  return { inTokens, outTokens, costUsd, sessionId };
 }
 
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