⚡️ Speed up function fibonacci by 124%

[codeflash-ai]

📄 124% (1.24x) speedup for fibonacci in code_to_optimize_ts/fibonacci.ts

⏱️ Runtime : 3.91 microseconds → 1.75 microsecondss (best of 250 runs)

📝 Explanation and details

The optimized code achieves a 124% speedup by replacing the exponential-time recursive algorithm with a linear-time iterative approach.

Key Changes:

• Eliminated recursive calls: The original code recursively computes fibonacci(n-1) + fibonacci(n-2), causing exponential growth in function calls—for fibonacci(10), this creates hundreds of redundant calculations.
• Iterative loop with state tracking: The optimized version uses two variables (prev and curr) to track the last two Fibonacci numbers, computing each value exactly once in a forward loop.

Why This Is Faster:

• Time complexity: O(2^n) → O(n). The original performs redundant recalculations (e.g., fibonacci(5) gets computed multiple times when calculating fibonacci(10)). The iterative version calculates each Fibonacci number exactly once.
• Space complexity: O(n) call stack → O(1). The recursive version builds a call stack proportional to n, while the iterative version uses only three variables regardless of input size.
• Reduced overhead: Eliminates function call overhead (stack frame allocation, parameter passing, return address management) which compounds with each recursive level.

Performance Impact:
Even at small values like n=10 (based on the ~4μs runtime suggesting modest input), the speedup is noticeable. For larger values (n>30), the difference becomes dramatic—exponential vs. linear growth means the original would take seconds while the optimized version remains sub-millisecond.

Best For:
This optimization excels with any n > 10, where the exponential cost of recursion becomes prohibitive. The iterative approach maintains consistent, predictable performance scaling.

✅ 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-mklolrdo and push.