Faster optimized frozen dictionary creation (2/n) #87630
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This reverts commit 204e175.
…oids a closure, index boundary checks and helps with inlining (7% gain) in case of hash set of integers it avoids renting and copying all integers to just have a copy of them
…ont (2-4% gain) * in CreateLengthBucketsFrozenDictionaryIfAppropriate iterate over array rather than dictionary * in OrdinalStringFrozenDictionary ctor avoid creating a copy of all entires (we already have a copy of keys)
…ength is the replacement)
adamsitnik
added
area-System.Collections
tenet-performance
ghost
assigned 
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Tagging subscribers to this area: @dotnet/area-system-collections Issue Details
LaunchCount=9 MemoryRandomization=True
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stephentoub
approved these changes
Jun 16, 2023
| _hashTable = FrozenHashTable.Create( | ||
| entries.Length, | ||
| index => entries[index] is T t ? Comparer.GetHashCode(t) : 0, | ||
| hashCodes, | ||
| (destIndex, srcIndex) => _items[destIndex] = entries[srcIndex], |
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Not entirely familiar with the implementation, but curious why we're doing delayed initialization for the _items array?
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It's not delayed, it's happening during the call to Create, which is helping to put the values in the right spot.
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FrozenHashTable.Createprovide the hashcodes, it eliminates a closure and boundary checks and one method call (7% gain)CreateLengthBucketsFrozenDictionaryIfAppropriateiterate over array rather than dictionaryOrdinalStringFrozenDictionaryctor avoid creating a copy of all entries (we already have a copy of keys)