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Implement a cache for the cosine computation in CheapRuler.

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This commit is contained in:
Phyks (Lucas Verney) 2018-11-21 15:29:57 +01:00
parent 665b7096e8
commit c78b56645c
5 changed files with 107 additions and 48 deletions
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5
brouter-core/src/main/java/btools/router/OsmPathElement.java
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@ -2,7 +2,7 @@ package btools.router;
import btools.mapaccess.OsmNode;
import btools.mapaccess.OsmPos;
import btools.util.CheapRuler;
import btools.util.CheapRulerSingleton;
import java.io.DataInput;
import java.io.DataOutput;
@ -78,7 +78,8 @@ public class OsmPathElement implements OsmPos
public final int calcDistance( OsmPos p )
{
return (int)(CheapRuler.distance(ilon, ilat, p.getILon(), p.getILat()) + 1.0 );
CheapRulerSingleton cr = CheapRulerSingleton.getInstance();
return (int)(cr.distance(ilon, ilat, p.getILon(), p.getILat()) + 1.0 );
}
public OsmPathElement origin;

5
brouter-mapaccess/src/main/java/btools/mapaccess/OsmNode.java
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@ -9,7 +9,7 @@ import btools.codec.MicroCache;
import btools.codec.MicroCache2;
import btools.expressions.BExpressionContextWay;
import btools.util.ByteArrayUnifier;
import btools.util.CheapRuler;
import btools.util.CheapRulerSingleton;
import btools.util.IByteArrayUnifier;
public class OsmNode extends OsmLink implements OsmPos
@ -103,7 +103,8 @@ public class OsmNode extends OsmLink implements OsmPos
public final int calcDistance( OsmPos p )
{
return (int) (CheapRuler.distance(ilon, ilat, p.getILon(), p.getILat()) + 1.0);
CheapRulerSingleton cr = CheapRulerSingleton.getInstance();
return (int) (cr.distance(ilon, ilat, p.getILon(), p.getILat()) + 1.0);
}
public String toString()

5
brouter-mem-router/src/main/java/btools/memrouter/OsmNodeP.java
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@ -6,7 +6,7 @@
package btools.memrouter;
import btools.mapaccess.OsmPos;
import btools.util.CheapRuler;
import btools.util.CheapRulerSingleton;
public class OsmNodeP extends OsmLinkP implements Comparable<OsmNodeP>, OsmPos
{
@ -103,7 +103,8 @@ public class OsmNodeP extends OsmLinkP implements Comparable<OsmNodeP>, OsmPos
@Override
public int calcDistance( OsmPos p )
{
return (int)(CheapRuler.distance(ilon, ilat, p.getILon(), p.getILat()) + 1.0 );
CheapRulerSingleton cr = CheapRulerSingleton.getInstance();
return (int)(cr.distance(ilon, ilat, p.getILon(), p.getILat()) + 1.0 );
}
@Override

42
brouter-util/src/main/java/btools/util/CheapRuler.java
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@ -1,42 +0,0 @@
package btools.util;
public final class CheapRuler {
/**
* Cheap-Ruler Java implementation
* See
* https://blog.mapbox.com/fast-geodesic-approximations-with-cheap-ruler-106f229ad016
* for more details.
*
* Original code is at https://github.com/mapbox/cheap-ruler under ISC license.
*/
static int KILOMETERS_TO_METERS = 1000;
static double ILATLNG_TO_LATLNG = 1e-6;
static double DEG_TO_RAD = Math.PI / 180.;
/*
* @param ilon1 Integer longitude for the start point. this is (longitude in degrees + 180) * 1e6.
* @param ilat1 Integer latitude for the start point, this is (latitude + 90) * 1e6.
* @param ilon2 Integer longitude for the end point, this is (longitude + 180) * 1e6.
* @param ilat2 Integer latitude for the end point, this is (latitude + 90) * 1e6.
*
* @note Integer longitude is ((longitude in degrees) + 180) * 1e6.
* Integer latitude is ((latitude in degrees) + 90) * 1e6.
*/
static public double distance(int ilon1, int ilat1, int ilon2, int ilat2) {
double lat1 = ilat1 * ILATLNG_TO_LATLNG - 90.; // Real latitude, in degrees
double cos = Math.cos(lat1 * DEG_TO_RAD);
double cos2 = 2 * cos * cos - 1;
double cos3 = 2 * cos * cos2 - cos;
double cos4 = 2 * cos * cos3 - cos2;
double cos5 = 2 * cos * cos4 - cos3;
// Multipliers for converting integer longitude and latitude into distance
// (http://1.usa.gov/1Wb1bv7)
double kx = (111.41513 * cos - 0.09455 * cos3 + 0.00012 * cos5) * ILATLNG_TO_LATLNG * KILOMETERS_TO_METERS;
double ky = (111.13209 - 0.56605 * cos2 + 0.0012 * cos4) * ILATLNG_TO_LATLNG * KILOMETERS_TO_METERS;
double dlat = (ilat1 - ilat2) * ky;
double dlon = (ilon1 - ilon2) * kx;
return Math.sqrt(dlat * dlat + dlon * dlon); // in m
}
}

98
brouter-util/src/main/java/btools/util/CheapRulerSingleton.java Normal file
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@ -0,0 +1,98 @@
package btools.util;
public final class CheapRulerSingleton {
/**
* Cheap-Ruler Java implementation
* See
* https://blog.mapbox.com/fast-geodesic-approximations-with-cheap-ruler-106f229ad016
* for more details.
*
* Original code is at https://github.com/mapbox/cheap-ruler under ISC license.
*
* This is implemented as a Singleton to have a unique cache for the cosine
* values across all the code.
*/
private static volatile CheapRulerSingleton instance = null;
// Conversion constants
private final static double ILATLNG_TO_LATLNG = 1e-6; // From integer to degrees
private final static int KILOMETERS_TO_METERS = 1000;
private final static double DEG_TO_RAD = Math.PI / 180.;
// Cosine cache constants
private final static int COS_CACHE_LENGTH = 8192;
private final static double COS_CACHE_MAX_DEGREES = 90.0;
// COS_CACHE_LENGTH cached values between 0 and COS_CACHE_MAX_DEGREES degrees.
double[] COS_CACHE = new double[COS_CACHE_LENGTH];
/**
* Helper to build the cache of cosine values.
*/
private void buildCosCache() {
double increment = DEG_TO_RAD * COS_CACHE_MAX_DEGREES / COS_CACHE_LENGTH;
for (int i = 0; i < COS_CACHE_LENGTH; i++) {
COS_CACHE[i] = Math.cos(i * increment);
}
}
private CheapRulerSingleton() {
super();
// Build the cache of cosine values.
buildCosCache();
}
/**
* Get an instance of this singleton class.
*/
public final static CheapRulerSingleton getInstance() {
if (CheapRulerSingleton.instance == null) {
synchronized(CheapRulerSingleton.class) {
if (CheapRulerSingleton.instance == null) {
CheapRulerSingleton.instance = new CheapRulerSingleton();
}
}
}
return CheapRulerSingleton.instance;
}
/**
* Helper to compute the cosine of an integer latitude.
*/
private double cosLat(int ilat) {
double latDegrees = ilat * ILATLNG_TO_LATLNG;
if (ilat > 90000000) {
// Use the symmetry of the cosine.
latDegrees -= 90;
}
return COS_CACHE[(int) (latDegrees * COS_CACHE_LENGTH / COS_CACHE_MAX_DEGREES)];
}
/**
* Compute the distance (in meters) between two points represented by their
* (integer) latitude and longitude.
*
* @param ilon1 Integer longitude for the start point. this is (longitude in degrees + 180) * 1e6.
* @param ilat1 Integer latitude for the start point, this is (latitude + 90) * 1e6.
* @param ilon2 Integer longitude for the end point, this is (longitude + 180) * 1e6.
* @param ilat2 Integer latitude for the end point, this is (latitude + 90) * 1e6.
*
* @note Integer longitude is ((longitude in degrees) + 180) * 1e6.
* Integer latitude is ((latitude in degrees) + 90) * 1e6.
*/
public double distance(int ilon1, int ilat1, int ilon2, int ilat2) {
double cos = cosLat(ilat1);
double cos2 = 2 * cos * cos - 1;
double cos3 = 2 * cos * cos2 - cos;
double cos4 = 2 * cos * cos3 - cos2;
double cos5 = 2 * cos * cos4 - cos3;
// Multipliers for converting integer longitude and latitude into distance
// (http://1.usa.gov/1Wb1bv7)
double kx = (111.41513 * cos - 0.09455 * cos3 + 0.00012 * cos5) * ILATLNG_TO_LATLNG * KILOMETERS_TO_METERS;
double ky = (111.13209 - 0.56605 * cos2 + 0.0012 * cos4) * ILATLNG_TO_LATLNG * KILOMETERS_TO_METERS;
double dlat = (ilat1 - ilat2) * ky;
double dlon = (ilon1 - ilon2) * kx;
return Math.sqrt(dlat * dlat + dlon * dlon); // in m
}
}