From a45d33619893e9f7a3e947278a908f770b307884 Mon Sep 17 00:00:00 2001
From: Luc Maisonobe <luc@orekit.org>
Date: Mon, 16 Feb 2015 17:41:33 +0100
Subject: [PATCH] Simplified tiles cache.
---
.../org/orekit/rugged/raster/TilesCache.java | 324 ++----------------
.../orekit/rugged/raster/TilesCacheTest.java | 7 +
2 files changed, 36 insertions(+), 295 deletions(-)
diff --git a/src/main/java/org/orekit/rugged/raster/TilesCache.java b/src/main/java/org/orekit/rugged/raster/TilesCache.java
index d8174a1c..dbcc447c 100644
--- a/src/main/java/org/orekit/rugged/raster/TilesCache.java
+++ b/src/main/java/org/orekit/rugged/raster/TilesCache.java
@@ -16,18 +16,11 @@
*/
package org.orekit.rugged.raster;
-import java.io.Serializable;
import java.lang.reflect.Array;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.Comparator;
-import java.util.Iterator;
-import java.util.List;
import org.apache.commons.math3.util.FastMath;
import org.orekit.rugged.errors.RuggedException;
import org.orekit.rugged.errors.RuggedMessages;
-import org.orekit.rugged.raster.Tile.Location;
/** Cache for Digital Elevation Model {@link Tile tiles}.
* <p>
@@ -44,14 +37,8 @@ public class TilesCache<T extends Tile> {
/** Updater for retrieving tiles data. */
private final TileUpdater updater;
- /** Search optimized cache. */
- private List<TilesStrip> searchCache;
-
- /** Eviction queue. */
- private T[] evictionQueue;
-
- /** Index for next tile. */
- private int next;
+ /** Cache. */
+ private final T[] tiles;
/** Simple constructor.
* @param factory factory for creating empty tiles
@@ -60,12 +47,10 @@ public class TilesCache<T extends Tile> {
*/
public TilesCache(final TileFactory<T> factory, final TileUpdater updater, final int maxTiles) {
this.factory = factory;
- this.updater = updater;
- this.searchCache = new ArrayList<TilesStrip>();
+ this.updater = updater;
@SuppressWarnings("unchecked")
- final T[] array = (T[]) Array.newInstance(Tile.class, maxTiles + 1);
- this.evictionQueue = array;
- this.next = 0;
+ final T[] array = (T[]) Array.newInstance(Tile.class, maxTiles);
+ this.tiles = array;
}
/** Get the tile covering a ground point.
@@ -76,296 +61,45 @@ public class TilesCache<T extends Tile> {
*/
public T getTile(final double latitude, final double longitude)
throws RuggedException {
- final T tile = getStrip(latitude, longitude).getTile(latitude, longitude);
- if (tile.getLocation(latitude, longitude) != Tile.Location.HAS_INTERPOLATION_NEIGHBORS) {
- // this should happen only if user set up an inconsistent TileUpdater
- throw new RuggedException(RuggedMessages.TILE_WITHOUT_REQUIRED_NEIGHBORS_SELECTED,
- FastMath.toDegrees(latitude),
- FastMath.toDegrees(longitude));
- }
- return tile;
- }
-
- /** Create a tile covering a ground point.
- * @param latitude latitude of the point
- * @param longitude longitude of the point
- * @return new tile covering the point
- * @exception RuggedException if tile cannot be updated
- */
- private T createTile(final double latitude, final double longitude)
- throws RuggedException {
-
- // create the tile and retrieve its data
- final T tile = factory.createTile();
- updater.updateTile(latitude, longitude, tile);
- tile.tileUpdateCompleted();
-
- return tile;
-
- }
-
- /** Append newly created tile at the end of the eviction queue.
- * @param tile tile to append to queue
- */
- private void appendToEvictionQueue(final T tile) {
-
- evictionQueue[next] = tile;
- next = (next + 1) % evictionQueue.length;
-
- if (evictionQueue[next] != null) {
- // the cache is full, we need to evict one tile
- // from both the eviction cache and the search cache
- for (final Iterator<TilesStrip> iterator = searchCache.iterator(); iterator.hasNext();) {
- if (iterator.next().removeTile(evictionQueue[next])) {
- evictionQueue[next] = null;
- return;
- }
- }
- }
-
- }
-
- /** Get a strip covering a ground point.
- * @param latitude ground point latitude
- * @param longitude ground point longitude
- * @return strip covering the ground point
- * @exception RuggedException if tile cannot be updated
- */
- private TilesStrip getStrip(final double latitude, final double longitude)
- throws RuggedException {
-
- // look for a strip at the specified latitude
- final int index = Collections.binarySearch(searchCache, new BasicLatitudeProvider(latitude),
- new LatitudeComparator());
- if (index >= 0) {
- // rare case, the latitude is an exact maximum latitude for a strip
- return searchCache.get(index);
- } else {
- final int insertionPoint = -(index + 1);
+ for (int i = 0; i < tiles.length; ++i) {
+ final T tile = tiles[i];
+ if (tile != null && tile.getLocation(latitude, longitude) == Tile.Location.HAS_INTERPOLATION_NEIGHBORS) {
+ // we have found the tile in the cache
- if (insertionPoint < searchCache.size()) {
- final TilesStrip strip = searchCache.get(insertionPoint);
- if (strip.covers(latitude)) {
- // we have found an existing strip
- return strip;
+ // put it on the front as it becomes the most recently used
+ while (i > 0) {
+ tiles[i] = tiles[i - 1];
+ --i;
}
- }
-
- // no existing strip covers the specified latitude, we need to create a new one
- final T tile = createTile(latitude, longitude);
- final TilesStrip strip = new TilesStrip(tile);
- searchCache.add(insertionPoint, strip);
- appendToEvictionQueue(tile);
- return strip;
-
- }
-
- }
-
- /** Interface for retrieving latitude. */
- private interface LatitudeProvider {
-
- /** Get latitude.
- * @return latitude
- */
- double getLatitude();
-
- }
-
- /** Basic implementation of {@link LatitudeProvider}. */
- private static class BasicLatitudeProvider implements LatitudeProvider {
-
- /** Latitude. */
- private final double latitude;
-
- /** Simple constructor.
- * @param latitude latitude
- */
- public BasicLatitudeProvider(final double latitude) {
- this.latitude = latitude;
- }
-
- /** {@inheritDoc} */
- @Override
- public double getLatitude() {
- return latitude;
- }
-
- }
-
- /** Interface for retrieving longitude. */
- private interface LongitudeProvider {
+ tiles[0] = tile;
- /** Get longitude.
- * @return longitude
- */
- double getLongitude();
-
- }
-
- /** Basic implementation of {@link LongitudeProvider}. */
- private static class BasicLongitudeProvider implements LongitudeProvider {
-
- /** Longitude. */
- private final double longitude;
-
- /** Simple constructor.
- * @param longitude longitude
- */
- public BasicLongitudeProvider(final double longitude) {
- this.longitude = longitude;
- }
-
- /** {@inheritDoc} */
- @Override
- public double getLongitude() {
- return longitude;
- }
-
- }
-
- /** Strip of tiles for a given latitude. */
- private class TilesStrip implements LatitudeProvider {
-
- /** Minimum latitude. */
- private final double minLatitude;
-
- /** Maximum latitude. */
- private final double maxLatitude;
-
- /** Tiles list. */
- private final List<TileDecorator> tiles;
-
- /** Simple constructor.
- * @param tile first tile to insert in the strip
- */
- public TilesStrip(final T tile) {
- minLatitude = tile.getMinimumLatitude();
- maxLatitude = tile.getMaximumLatitude();
- tiles = new ArrayList<TileDecorator>();
- tiles.add(new TileDecorator(tile));
- }
-
- /** Check if the strip covers a specified latitude.
- * @param latitude latitude to check
- * @return true if the strip covers the latitude
- */
- public boolean covers(final double latitude) {
- return (minLatitude <= latitude) && (maxLatitude >= latitude);
- }
-
- /** {@inheritDoc} */
- @Override
- public double getLatitude() {
- return maxLatitude;
- }
-
- /** Get a tile covering a ground point.
- * @param latitude ground point latitude
- * @param longitude ground point longitude
- * @return strip covering the ground point
- * @exception RuggedException if tile cannot be updated
- */
- public T getTile(final double latitude, final double longitude)
- throws RuggedException {
-
- // look for a tile at the specified longitude
- final int index = Collections.binarySearch(tiles, new BasicLongitudeProvider(longitude),
- new LongitudeComparator());
- if (index >= 0) {
- // rare case, the longitude is an exact maximum longitude for a tile
- return tiles.get(index).getTile();
- } else {
-
- final int insertionPoint = -(index + 1);
-
- if (insertionPoint < tiles.size()) {
- final T tile = tiles.get(insertionPoint).getTile();
- if (tile.getLocation(latitude, longitude) == Location.HAS_INTERPOLATION_NEIGHBORS) {
- // we have found an existing tile
- return tile;
- }
- }
-
- // no existing tile covers the specified ground point, we need to create a new one
- final T tile = createTile(latitude, longitude);
- tiles.add(insertionPoint, new TileDecorator(tile));
- appendToEvictionQueue(tile);
return tile;
- }
- }
-
- /** Remove a tile from the strip.
- * @param tile tile to remove
- * @return true if the tile has been removed
- */
- public boolean removeTile(final Tile tile) {
- for (final Iterator<TileDecorator> iterator = tiles.iterator(); iterator.hasNext();) {
- if (iterator.next().getTile() == tile) {
- iterator.remove();
- return true;
- }
}
- return false;
- }
-
- }
-
- /** Decorator for tiles, implementing {@link LongitudeProvider}. */
- private class TileDecorator implements LongitudeProvider {
-
- /** Underlying tile. */
- private final T tile;
-
- /** Simple constructor.
- * @param tile tile to decorate
- */
- public TileDecorator(final T tile) {
- this.tile = tile;
}
- /** Get the underlying tile.
- * @return underlying tile
- */
- public T getTile() {
- return tile;
- }
+ // none of the tiles in the cache covers the specified points
- /** {@inheritDoc} */
- @Override
- public double getLongitude() {
- return tile.getMaximumLongitude();
+ // make some room in the cache, possibly evicting the least recently used one
+ for (int i = tiles.length - 1; i > 0; --i) {
+ tiles[i] = tiles[i - 1];
}
- }
-
- /** Comparator for sorting with respect to latitude. */
- private static class LatitudeComparator implements Comparator<LatitudeProvider>, Serializable {
-
- /** Serializable UID. */
- private static final long serialVersionUID = 20141212L;
+ // create the tile and retrieve its data
+ final T tile = factory.createTile();
+ updater.updateTile(latitude, longitude, tile);
+ tile.tileUpdateCompleted();
- /** {@inheritDoc} */
- @Override
- public int compare(final LatitudeProvider o1, final LatitudeProvider o2) {
- return Double.compare(o1.getLatitude(), o2.getLatitude());
+ if (tile.getLocation(latitude, longitude) != Tile.Location.HAS_INTERPOLATION_NEIGHBORS) {
+ // this should happen only if user set up an inconsistent TileUpdater
+ throw new RuggedException(RuggedMessages.TILE_WITHOUT_REQUIRED_NEIGHBORS_SELECTED,
+ FastMath.toDegrees(latitude),
+ FastMath.toDegrees(longitude));
}
- }
-
- /** Comparator for sorting with respect to longitude. */
- private static class LongitudeComparator implements Comparator<LongitudeProvider>, Serializable {
-
- /** Serializable UID. */
- private static final long serialVersionUID = 20141212L;
-
- /** {@inheritDoc} */
- @Override
- public int compare(final LongitudeProvider o1, final LongitudeProvider o2) {
- return Double.compare(o1.getLongitude(), o2.getLongitude());
- }
+ tiles[0] = tile;
+ return tile;
}
diff --git a/src/test/java/org/orekit/rugged/raster/TilesCacheTest.java b/src/test/java/org/orekit/rugged/raster/TilesCacheTest.java
index 26d1f5f4..2863e5e7 100644
--- a/src/test/java/org/orekit/rugged/raster/TilesCacheTest.java
+++ b/src/test/java/org/orekit/rugged/raster/TilesCacheTest.java
@@ -65,6 +65,13 @@ public class TilesCacheTest {
}
Assert.assertEquals(12, factory.getCount());
+ // ensure the (0.0, 0.0) tile is the least recently used one
+ for (int i = 0; i < 4; ++i) {
+ for (int j = 0; j < 3; ++j) {
+ cache.getTile(FastMath.toRadians(0.5 + j), FastMath.toRadians(0.5 + i));
+ }
+ }
+
// ask for one point outside of the covered area, to evict the (0.0, 0.0) tile
cache.getTile(FastMath.toRadians(20.5), FastMath.toRadians(30.5));
Assert.assertEquals(13, factory.getCount());
--
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