Matching - Remove unnecessary enumerations

[zabeen]

Example 1

Atlas/Atlas.MatchingAlgorithm/Services/Search/SearchService.cs

Line 80 in 358ca2e

var reifiedScoredMatches = scoredMatches.DistinctBy(m => m.MatchResult.DonorId).ToList();

• .ToList() will load all matches into memory, might be hundreds of 1000s of donors.
• Also, why is DistinctBy() being applied to scored results set?
  • must be something to do with sub-search logic, as it was added at same time

Example 2

Atlas/Atlas.MatchingAlgorithm/Services/Search/Matching/DonorMatchingService.cs

Line 126 in 4b91dea

var donorIds = donorBatch.Keys.ToHashSet();

-- I'd propose eliminate this, Dictionary.ContainsKey works as fast as HashSet.Contains do. But taking into consideration batch size, it worth save 5Mb RAM and some CPU time spent on copying data just for fitting to type HashSet<T>