⚡️ Speed up method Fibonacci.fibonacci by 2,036%#2022
Merged
claude[bot] merged 1 commit intodocs/tracer/javafrom Apr 9, 2026
Merged
⚡️ Speed up method Fibonacci.fibonacci by 2,036%#2022claude[bot] merged 1 commit intodocs/tracer/javafrom
Fibonacci.fibonacci by 2,036%#2022claude[bot] merged 1 commit intodocs/tracer/javafrom
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The recursive implementation was replaced with an iterative fast-doubling algorithm that computes Fibonacci(n) in O(log n) time by processing the bits of n and applying matrix-exponentiation doubling formulas (F(2k) = F(k)*(2*F(k+1) - F(k)) and F(2k+1) = F(k+1)² + F(k)²), eliminating the exponential O(2^n) recursive call tree that dominated original runtime at 32.5% per the profiler. This cuts execution time from 3.81 ms to 179 µs (20× speedup) by avoiding redundant subproblem recomputation and deep call stacks. The optimization incurs no regressions in correctness, maintains identical exception behavior, and scales to larger n values that would timeout under naive recursion.
This was referenced Apr 9, 2026
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📄 2,036% (20.36x) speedup for
Fibonacci.fibonacciincode_to_optimize/java/src/main/java/com/example/Fibonacci.java⏱️ Runtime :
3.81 milliseconds→179 microseconds(best of79runs)📝 Explanation and details
The recursive implementation was replaced with an iterative fast-doubling algorithm that computes Fibonacci(n) in O(log n) time by processing the bits of n and applying matrix-exponentiation doubling formulas (F(2k) = F(k)(2F(k+1) - F(k)) and F(2k+1) = F(k+1)² + F(k)²), eliminating the exponential O(2^n) recursive call tree that dominated original runtime at 32.5% per the profiler. This cuts execution time from 3.81 ms to 179 µs (20× speedup) by avoiding redundant subproblem recomputation and deep call stacks. The optimization incurs no regressions in correctness, maintains identical exception behavior, and scales to larger n values that would timeout under naive recursion.
✅ Correctness verification report:
⏪ Click to see Replay Tests
To edit these changes
git checkout codeflash/optimize-Fibonacci.fibonacci-mnqq81k5and push.