⚡️ Speed up function fibonacci by 138%

[codeflash-ai]

📄 138% (1.38x) speedup for fibonacci in code_to_optimize_ts/fibonacci.ts

⏱️ Runtime : 3.96 microseconds → 1.66 microsecondss (best of 250 runs)

📝 Explanation and details

The optimized code achieves a 137% speedup by replacing the recursive algorithm with an iterative approach. Here's why this matters:

What changed:

• Eliminated recursive calls: The original uses naive recursion with exponential O(2^n) time complexity, making redundant calculations for the same Fibonacci values repeatedly.
• Introduced iterative loop: The optimized version uses a simple for-loop with two variables (prev, curr) to track consecutive Fibonacci numbers, achieving O(n) time complexity.

Why it's faster:

1. Avoided exponential explosion: For fibonacci(n), the recursive version makes ~2^n function calls due to overlapping subproblems. For example, fibonacci(5) recalculates fibonacci(3) twice and fibonacci(2) three times.
2. Reduced call stack overhead: Each recursive call adds overhead for function invocation and stack frame management. The iterative version eliminates this entirely.
3. Linear operations: The loop executes exactly n-1 iterations with simple arithmetic operations, making it dramatically more efficient.

Line profiler evidence:

• Original: 1200 hits on the function entry (line 12), showing extensive recursion
• Optimized: Only 19 hits on line 12, confirming minimal function calls
• The loop body (lines 20-22) shows 42-43 hits total, indicating efficient linear traversal

Performance impact:
This optimization scales exponentially better with larger n values. While the speedup is 137% for the tested inputs (reducing runtime from 3.96µs to 1.66µs), the gains become massive for larger Fibonacci numbers—potentially reducing seconds or minutes to milliseconds. The optimization is particularly beneficial if this function is called in hot paths or with varying input sizes.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	✅ 22 Passed
🌀 Generated Regression Tests	🔘 None Found
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

⚙️ Click to see Existing Unit Tests

To edit these changes git checkout codeflash/optimize-fibonacci-mklovcbp and push.