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perf: track infected nodes in SIR simulation instead of scanning all vertices - #107
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…vertices The SIR simulateSIR() method previously iterated all V vertices twice per round: once to find infected nodes for spreading, and once for recovery checks, plus a third pass to check if any infected remain. Replace with an explicit currentlyInfected set that is maintained incrementally. This reduces per-round cost from O(V) to O(|infected|) for the recovery check and termination test, which is significant for large sparse graphs where only a small fraction of nodes are infected at any given time. The infection spreading loop also benefits since it now only iterates currently infected nodes. This is especially impactful during Monte Carlo simulations where simulateSIR is called thousands of times.
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Summary
Optimizes the SIR epidemic simulation by maintaining an explicit \currentlyInfected\ set instead of scanning all V vertices each round.
Problem
The previous implementation had three O(V) passes per simulation round:
For large graphs (thousands of nodes) with low infection rates, most of these iterations were wasted checking susceptible/recovered nodes.
Solution
Track the set of currently infected nodes incrementally:
This reduces per-round cost from O(V) to O(|infected| * avg_degree) for spreading + O(|infected|) for recovery, which is significant when |infected| << V.
Impact
Especially impactful during Monte Carlo simulations (\monteCarlo()) where \simulateSIR\ is called thousands of times. For a 10,000-node graph with 100 trials, this eliminates millions of unnecessary state lookups.