geos::index::quadtree::IntervalSize Class Reference

Provides a test for whether an interval is so small it should be considered as zero for the purposes of inserting it into a binary tree. More...

#include <IntervalSize.h>

Static Public Member Functions
static bool	isZeroWidth (double min, double max)

Static Public Attributes
static const int	MIN_BINARY_EXPONENT = -50

Detailed Description

Provides a test for whether an interval is so small it should be considered as zero for the purposes of inserting it into a binary tree.

The reason this check is necessary is that round-off error can cause the algorithm used to subdivide an interval to fail, by computing a midpoint value which does not lie strictly between the endpoints.

Member Function Documentation

isZeroWidth()

static bool geos::index::quadtree::IntervalSize::isZeroWidth ( double  min, double  max  )

static

Computes whether the interval [min, max] is effectively zero width. I.e. the width of the interval is so much less than the location of the interval that the midpoint of the interval cannot be represented precisely.

Member Data Documentation

MIN_BINARY_EXPONENT

const int geos::index::quadtree::IntervalSize::MIN_BINARY_EXPONENT = -50

static

This value is chosen to be a few powers of 2 less than the number of bits available in the double representation (i.e. 53). This should allow enough extra precision for simple computations to be correct, at least for comparison purposes.

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The documentation for this class was generated from the following file:

• IntervalSize.h