Changeset 17516 in josm

Timestamp:

2021-02-21T23:50:53+01:00 (4 years ago)

Author:

wiktorn

Message:

Fine tune cache sizing

Reduce the cache size, by not counting the tiles that are overloaded for other
zoom levels. Overloaded tiles are only counted for current zoom level.

This reduces memory requirements for a layer, depending on the number of the
tiles shown by 20%-50%. Reduction is high for low number of tiles (when large
tiles or small screen is in use) and low for high number of tiles (when
small tiles or large screen is in use)

See: #20014, #20497

File:

• trunk/src/org/openstreetmap/josm/gui/layer/AbstractTileSourceLayer.java (modified) (2 diffs)

trunk/src/org/openstreetmap/josm/gui/layer/AbstractTileSourceLayer.java

@@ -641 +641 @@
         /**
          * As we can see part of the tile at the top and at the bottom, use Math.ceil(...) + 1 to accommodate for that
-         * Add another 2 tiles on each axis, as overloadTiles adds one tile in each direction that might be overloaded
-         *
-         * @see #overloadTiles()
          */
-        int maxYtiles = (int) Math.ceil((double) height / tileSize + 1) + 2;
-        int maxXtiles = (int) Math.ceil((double) width / tileSize + 1) + 2;
+        int maxYtiles = (int) Math.ceil((double) height / tileSize + 1);
+        int maxXtiles = (int) Math.ceil((double) width / tileSize + 1);
         int visibileTiles = maxXtiles * maxYtiles;
         /**
-         * Take into account ZOOM_OFFSET to calculate real number of tiles and multiply by 8, to cover all tiles, that might be
+         * Take into account ZOOM_OFFSET to calculate real number of tiles and multiply by 7, to cover all tiles, that might be
          * accessed when looking for tiles outside current zoom level.
          *
-         * The value should be sum(2^x for x in (-5 to 2))
+         * Currently we use otherZooms = {1, 2, -1, -2, -3, -4, -5}
          *
-         * Currently we use otherZooms = {1, 2, -1, -2, -3, -4, -5}
+         * The value should be sum(2^x for x in (-5 to 2)) - 1
+         * -1 to exclude current zoom level
          *
          * Check call to tryLoadFromDifferentZoom
@@ -660 +658 @@
          * @see #drawInViewArea((Graphics2D, MapView, ProjectionBounds)
          *
+         * Add +2 to maxYtiles / maxXtiles to add space in cache for extra tiles in current zoom level that are
+         * download by overloadTiles(). This is not added in computation of visibileTiles as this unnecessarily grow the cache size
+         * @see #overloadTiles()
          */
         int ret = (int) Math.ceil(
-                Math.pow(2d, ZOOM_OFFSET.get()) * visibileTiles // use offset to decide, how many tiles are visible
-                * 8);
-        Logging.info("AbstractTileSourceLayer: estimated tiles proccessed on current zoom level: {0}, estimated cache size: {1}",
-                visibileTiles, ret);
+                Math.pow(2d, ZOOM_OFFSET.get()) * // use offset to decide, how many tiles are visible
+                visibileTiles * 7 + // 7 to cover tiles from other zooms as described above
+                ((maxYtiles + 2) * (maxXtiles +2))); // to add as many tiles as they will be accessed on current zoom level
+        Logging.info("AbstractTileSourceLayer: estimated visibile tiles: {0}, estimated cache size: {1}", visibileTiles, ret);
         return ret;
     }