CODEWITHSUNDEEP
optaplanner
Marc Sol
Marc Sol

Reputation: 13

Why is score calculation speed faster for Construction Heuristics than Local Search?

Getting started with OptaPlanner (v.23.0.Final), I am experimenting with the CloudBalancing example. Using the IncrementalScoreCalculator Java class, I notice that the score calculation speed is much higher in the construction phase (>1M/sec) than in the local search phase (~50k/sec). How can this happen? Is the algorithm outside the score calculation included? That could explain the differnce, since the local search algorithm will spend much more time outside the score calculator than the construction algorithm.

Upvotes: 1

Views: 146

Answers (1)

Geoffrey De Smet
Geoffrey De Smet

Reputation: 27312

Two reasons:

1) The construction Heuristic starts with no processes assigned to a computer, so all Process.getComputer() is null. Most constraints match on Processes for which computer != null, so they short circuit and don't do any expensive joins, groupBy's, accumulates, etc. So an empty or a partially initialized solution evaluates much faster than a fully initialized one (which Local Search uses).

2) The CH's only do ChangeMove's. LS does more expensive moves including swap moves (twice as big) and pillar moves (n times as big). So the amount of delta impact to calculate per move is bigger in LS too.

Upvotes: 0

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