⚡️ Speed up method Fibonacci.fibonacci by 2,258%

[codeflash-ai]

📄 2,258% (22.58x) speedup for Fibonacci.fibonacci in code_to_optimize/java/src/main/java/com/example/Fibonacci.java

⏱️ Runtime : 3.33 milliseconds → 141 microseconds (best of 89 runs)

📝 Explanation and details

The naive recursive implementation was replaced with an iterative fast-doubling algorithm that computes Fibonacci numbers in O(log n) time instead of O(2^n), reducing the function from 2.74 million calls (for n=30) to just 417 calls by eliminating exponential branching and redundant subproblem recomputation. The optimized version processes bits of n left-to-right using matrix identities F(2k) = F(k)·(2F(k+1) − F(k)) and F(2k+1) = F(k)² + F(k+1)², avoiding all recursion overhead and achieving a 23× runtime speedup (3.33 ms → 141 µs). Line profiler confirms the original spent 33% of time in recursive calls alone, now eliminated entirely with O(1) space instead of O(n) stack depth.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	🔘 None Found
⏪ Replay Tests	✅ 239 Passed
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	Coverage data not available

⏪ Click to see Replay Tests

To edit these changes git checkout codeflash/optimize-Fibonacci.fibonacci-mnt4z1l0 and push.

[KRRT7]

Closing: opened by CI workflow that shouldn't create PRs.