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Quad Trees (cont)

Basis for the partitioning:
  • a quadrant that has no sub-partitions is a leaf quadrant
  • each leaf quadrant maps to a single data page
  • subdivide until points in each quadrant fit into one data page
  • ideal: same number of points in each leaf quadrant (balanced)
  • point density varies over space
    different regions require different levels of partitioning
  • this means that the tree is not necessarily balanced
Note: effective for d≤5, ok for 6≤d≤10, ineffective for d>10