private static List <Neighbor> GetNeighborsByDistance(LeafNode leafNode, IDictionary <int, List <LeafNode> > buckets, IDistanceMetric distanceMetric)
{
var neighbors = distanceMetric.SignificantCoordinates(leafNode.Coords)
// Get every node with at least one shared match in common
.SelectMany(coord => buckets.TryGetValue(coord, out var bucket) ? bucket : Enumerable.Empty <LeafNode>())
// We only need one direction A -> B (not also B -> A) since we're ultimately going to look at the smallest distances.
.Where(neighborNode => neighborNode.Index < leafNode.Index)
// Make sure that each node is considered only once (might have been in more than one bucket if more than one shared match in common.
.Distinct()
.Select(neighborNode => new Neighbor(neighborNode, leafNode))
.LowestN(neighbor => neighbor.DistanceSquared, _maxNeighbors)
.ToList();
return(neighbors);
}
private static async Task CalculateNeighborsAsync(List <LeafNode> leafNodesAll, List <LeafNode> leafNodesToRecalculate, IDistanceMetric distanceMetric, ProgressData progressData)
{
var buckets = leafNodesAll
.SelectMany(leafNode => distanceMetric.SignificantCoordinates(leafNode.Coords).Select(coord => new { Coord = coord, LeafNode = leafNode }))
.GroupBy(pair => pair.Coord, pair => pair.LeafNode)
.ToDictionary(g => g.Key, g => g.ToList());
var calculateNeighborsByDistanceTasks = leafNodesToRecalculate.Select(async leafNode =>
{
leafNode.NeighborsByDistance = await Task.Run(() => GetNeighborsByDistance(leafNode, buckets, distanceMetric));
progressData?.Increment();
});
await Task.WhenAll(calculateNeighborsByDistanceTasks);
}
