class Geospatial::Hilbert::Curve
Attributes
dimensions[R]
order[R]
scale[R]
Public Class Methods
new(dimensions, order = 30)
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# File lib/geospatial/hilbert/curve.rb, line 27 def initialize(dimensions, order = 30) raise ArgumentError("Order #{order} must be positive integer!") unless order >= 1 # Order is the number of levels of the curve, which is equivalent to the number of bits per dimension. @order = order @scale = 2**@order @dimensions = dimensions * @scale @origin = dimensions.origin @size = dimensions.size end
Public Instance Methods
bit_width()
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# File lib/geospatial/hilbert/curve.rb, line 62 def bit_width @dimensions.count end
map(coordinates)
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# File lib/geospatial/hilbert/curve.rb, line 92 def map(coordinates) axes = @dimensions.map(coordinates).map(&:floor) index = OrdinalIndex.new(axes, @order) return index.to_hilbert.to_i end
origin()
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# File lib/geospatial/hilbert/curve.rb, line 43 def origin @dimensions.origin end
size()
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# File lib/geospatial/hilbert/curve.rb, line 47 def size @dimensions.size end
to_s()
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# File lib/geospatial/hilbert/curve.rb, line 51 def to_s "\#<#{self.class} order=#{@order} dimensions=#{@dimensions}>" end
traverse(&block)
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This is a helper entry point for traversing Hilbert
space.
# File lib/geospatial/hilbert/curve.rb, line 56 def traverse(&block) return to_enum(:traverse) unless block_given? traverse_recurse(@order-1, 0, 0, self.origin, self.size, &block) end
traverse_recurse(order, mask, value, origin, size) { |child_origin, half_size, prefix, order| ... }
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Traversal enumerates all regions of a curve, top-down.
# File lib/geospatial/hilbert/curve.rb, line 67 def traverse_recurse(order, mask, value, origin, size, &block) half_size = size.collect{|value| value * 0.5}.freeze prefix_mask = (1 << order) | mask (2**bit_width).times do |prefix| # These both do the same thing, not sure which one is faster: child_value = (value << @dimensions.count) | prefix prefix = child_value << (order*bit_width) index = HilbertIndex.from_integral(prefix, bit_width, @order).to_ordinal index = index & prefix_mask child_origin = @dimensions.unmap(index.axes).freeze # puts "yield(#{child_origin}, #{half_size}, #{prefix}, #{order})" # We avoid calling traverse_recurse simply to hit the callback on the leaf nodes: result = yield child_origin, half_size, prefix, order if order > 0 and result != :skip self.traverse_recurse(order - 1, prefix_mask, child_value, child_origin, half_size, &block) end end end
unmap(value)
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# File lib/geospatial/hilbert/curve.rb, line 100 def unmap(value) index = HilbertIndex.from_integral(value, @dimensions.count, @order) return @dimensions.unmap(index.to_ordinal.axes) end