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perf: reduce computeStress() memory from O(V²) to O(V) - #90
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The previous implementation pre-computed all-pairs BFS shortest paths into a Map<String, Map<String, Integer>> before iterating over pairs. For a graph with V vertices this allocates V HashMap instances with up to V entries each, plus V² boxed Integer objects — all held in memory simultaneously. This change computes BFS one source vertex at a time and discards the distance map after processing, keeping only one BFS result alive at any point. The algorithmic complexity is unchanged (still O(V*(V+E))) but peak heap usage drops from O(V²) to O(V+E), which matters for graphs with thousands of nodes where the stress metric is most useful.
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Closing: superseded or conflicting with newer changes already on main/master. |
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The previous implementation pre-computed all-pairs BFS shortest paths into a nested Map before iterating over pairs. For a graph with V vertices this allocates V HashMap instances with up to V entries each, plus V┬▓ boxed Integer objects ΓÇö all held in memory simultaneously. This change computes BFS one source vertex at a time and discards the distance map after processing, keeping only one BFS result alive at any point. The algorithmic complexity is unchanged (still O(V*(V+E))) but peak heap usage drops from O(V┬▓) to O(V+E), which matters for graphs with thousands of nodes where the stress metric is most useful.