com.vividsolutions.jts.index.quadtree.IntervalSize Maven / Gradle / Ivy
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/*
* The JTS Topology Suite is a collection of Java classes that
* implement the fundamental operations required to validate a given
* geo-spatial data set to a known topological specification.
*
* Copyright (C) 2001 Vivid Solutions
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* For more information, contact:
*
* Vivid Solutions
* Suite #1A
* 2328 Government Street
* Victoria BC V8T 5G5
* Canada
*
* (250)385-6040
* www.vividsolutions.com
*/
package com.vividsolutions.jts.index.quadtree;
/**
* 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.
*
* @version 1.7
*/
public class IntervalSize {
/**
* 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.
*/
public static final int MIN_BINARY_EXPONENT = -50;
/**
* 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.
*/
public static boolean isZeroWidth(double min, double max)
{
double width = max - min;
if (width == 0.0) return true;
double maxAbs = Math.max(Math.abs(min), Math.abs(max));
double scaledInterval = width / maxAbs;
int level = DoubleBits.exponent(scaledInterval);
return level <= MIN_BINARY_EXPONENT;
}
}