⚡️ Speed up method Algorithms.fibonacci by 23%

[codeflash-ai]

📄 23% (0.23x) speedup for Algorithms.fibonacci in code_to_optimize/java/src/main/java/com/example/Algorithms.java

⏱️ Runtime : 4.81 milliseconds → 3.90 milliseconds (best of 5 runs)

📝 Explanation and details

The optimized code achieves a 23% runtime improvement by replacing the exponential-time recursive Fibonacci implementation with an iterative approach that uses only two primitive long variables.

Key Performance Gains:

1. Eliminated Exponential Complexity: The original recursive implementation has O(2^n) time complexity due to repeated recalculation of the same Fibonacci numbers. The optimized version computes each number exactly once in O(n) time, providing dramatic speedups especially as n increases.

2. Removed Call Stack Overhead: The recursive approach incurs function call overhead and builds a call stack of depth O(n). The iterative solution eliminates all recursion, using only a simple for-loop with O(1) space complexity.

3. Cache-Friendly Memory Access: The optimized code uses only three local primitive variables (prev, curr, next) that fit entirely in CPU registers, avoiding the memory fragmentation and cache misses associated with deep recursion.

4. Reduced Memory Pressure: By eliminating the recursive call stack, the optimization dramatically reduces memory usage from O(n) to O(1), which also reduces garbage collection pressure and improves overall system performance.

The 23% speedup observed at 4.81ms → 3.90ms runtime represents the performance gain even for relatively small n values where both approaches complete quickly. For larger Fibonacci numbers, the speedup would be exponentially more dramatic—what takes seconds recursively completes in microseconds iteratively. This optimization is particularly valuable if fibonacci() is called frequently or with varying input sizes, as it provides consistent O(n) performance regardless of input magnitude.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	✅ 12 Passed
🌀 Generated Regression Tests	🔘 None Found
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	No coverage data found for fibonacci

⚙️ Click to see Existing Unit Tests

To edit these changes git checkout codeflash/optimize-Algorithms.fibonacci-mlbe9ts7 and push.