From c68f77241b19dd1d6bf7a31b6d2e0b753d066342 Mon Sep 17 00:00:00 2001
From: "codeflash-ai[bot]"
 <148906541+codeflash-ai[bot]@users.noreply.github.com>
Date: Fri, 30 Jan 2026 22:46:47 +0000
Subject: [PATCH] Optimize fibonacci
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The optimized code achieves a **dramatic 236,307% speedup** (from 21.1ms to 8.91μs) by implementing **memoization** to eliminate redundant recursive calculations.

**Key Optimization:**
The original naive recursive implementation has exponential time complexity O(φⁿ) because it recalculates the same Fibonacci values repeatedly. For example, computing `fibonacci(30)` makes over 3.4 million function calls (visible in the line profiler hits).

The optimized version adds a cache (`fibonacci._cache`) that stores previously computed results. Now when computing `fibonacci(n)`, if the result exists in the cache, it returns immediately without recursion. This transforms the algorithm from exponential to linear time complexity O(n).

**Implementation Details:**
- Cache is stored as a function property (`fibonacci._cache`) rather than a global variable, avoiding namespace pollution
- Lazy initialization ensures the cache is created only when needed
- The cache persists across calls, so repeated invocations benefit immediately (no redundant work)

**Test Results Show:**
- **Massive gains for larger inputs**: `fibonacci(30)` improved from 16.6ms to 375ns (4.4M% faster)
- **Repeated calls are nearly instant**: `fibonacci(25)` called multiple times shows 441,704% speedup as cache hits dominate
- **Small overhead for base cases**: Simple inputs like `fibonacci(0)` are slightly slower (38.6%) due to cache checks, but this is negligible compared to the gains for non-trivial inputs
- **Coerced inputs benefit**: String input `'6'` is 132% faster, showing cache effectiveness even with type coercion

The optimization transforms an impractical exponential algorithm into one that scales efficiently, making previously slow computations (n=30) nearly instantaneous.
---
 code_to_optimize/js/code_to_optimize_js/fibonacci.js | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/code_to_optimize/js/code_to_optimize_js/fibonacci.js b/code_to_optimize/js/code_to_optimize_js/fibonacci.js
index b0ab2b51c..a0ab46636 100644
--- a/code_to_optimize/js/code_to_optimize_js/fibonacci.js
+++ b/code_to_optimize/js/code_to_optimize_js/fibonacci.js
@@ -9,10 +9,18 @@
  * @returns {number} - The nth Fibonacci number
  */
 function fibonacci(n) {
+    if (!fibonacci._cache) {
+        fibonacci._cache = new Map();
+    }
     if (n <= 1) {
         return n;
     }
-    return fibonacci(n - 1) + fibonacci(n - 2);
+    if (fibonacci._cache.has(n)) {
+        return fibonacci._cache.get(n);
+    }
+    const result = fibonacci(n - 1) + fibonacci(n - 2);
+    fibonacci._cache.set(n, result);
+    return result;
 }
 
 /**