Skip to content

Minor improvements for AddHashElement #43

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Minor improvements for AddHashElement #43

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
21 changes: 13 additions & 8 deletions CardinalityEstimation/CardinalityEstimator.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -111,7 +111,7 @@ public class CardinalityEstimator : ICardinalityEstimator<string>, ICardinalityE
/// <summary>
/// Lookup dictionary for the sparse representation of HLL buckets
/// </summary>
private IDictionary<ushort, byte> lookupSparse;
private Dictionary<ushort, byte> lookupSparse;

/// <summary>
/// Max number of elements to hold in the sparse representation before switching to dense
Expand Down Expand Up @@ -787,19 +787,24 @@ private bool AddElementHash(ulong hashCode)
if (isSparse)
{
lookupSparse.TryGetValue(substream, out byte prevRank);
lookupSparse[substream] = Math.Max(prevRank, sigma);
changed = changed || (prevRank != sigma && lookupSparse[substream] == sigma);
if (lookupSparse.Count > sparseMaxElements)
if (sigma > prevRank)
{
SwitchToDenseRepresentation();
lookupSparse[substream] = sigma;
if (lookupSparse.Count > sparseMaxElements)
{
SwitchToDenseRepresentation();
}
changed = true;
}
}
else
{
var prevMax = lookupDense[substream];
lookupDense[substream] = Math.Max(prevMax, sigma);
changed = changed || (prevMax != sigma && lookupDense[substream] == sigma);
ref var value = ref lookupDense[substream];
if (sigma > value)
{
value = sigma;
changed = true;
}
}
return changed;
}
Expand Down