Changeset 10915 in josm

Timestamp:

2016-08-29T18:21:41+02:00 (8 years ago)

Author:

michael2402

Message:

Trim interpolate in EastNorth/LatLon for performance and add comment explaining it. Added unit tests.

Location:

trunk

Files:

• src/org/openstreetmap/josm/data/coor/EastNorth.java (modified) (2 diffs)
• src/org/openstreetmap/josm/data/coor/LatLon.java (modified) (2 diffs)
• test/unit/org/openstreetmap/josm/data/coor/EastNorthTest.java (added)
• test/unit/org/openstreetmap/josm/data/coor/LatLonTest.java (modified) (1 diff)

trunk/src/org/openstreetmap/josm/data/coor/EastNorth.java

@@ -82 +82 @@
      */
     public EastNorth interpolate(EastNorth en2, double proportion) {
-        return new EastNorth(this.x + proportion * (en2.x - this.x),
-                this.y + proportion * (en2.y - this.y));
+        // this is an alternate form of this.x + proportion * (en2.x - this.x) that is slightly faster
+        return new EastNorth((1 - proportion) * this.x + proportion * en2.x,
+                (1 - proportion) * this.y + proportion * en2.y);
     }
 
@@ -92 +93 @@
      */
     public EastNorth getCenter(EastNorth en2) {
-        return new EastNorth((this.x + en2.x)/2.0, (this.y + en2.y)/2.0);
+        // The JIT will inline this for us, it is as fast as the normal /2 approach
+        return interpolate(en2, .5);
     }
 

trunk/src/org/openstreetmap/josm/data/coor/LatLon.java

@@ -427 +427 @@
      */
     public LatLon interpolate(LatLon ll2, double proportion) {
-        return new LatLon(this.lat() + proportion * (ll2.lat() - this.lat()),
-                this.lon() + proportion * (ll2.lon() - this.lon()));
+        // this is an alternate form of this.lat() + proportion * (ll2.lat() - this.lat()) that is slightly faster
+        return new LatLon((1 - proportion) * this.lat() + proportion * ll2.lat(),
+                (1 - proportion) * this.lon() + proportion * ll2.lon());
     }
 
@@ -437 +438 @@
      */
     public LatLon getCenter(LatLon ll2) {
+        // The JIT will inline this for us, it is as fast as the normal /2 approach
         return interpolate(ll2, .5);
     }

trunk/test/unit/org/openstreetmap/josm/data/coor/LatLonTest.java

@@ -165 +165 @@
         assertEquals("2115070.3250722", c.lonToString(CoordinateFormat.EAST_NORTH));
     }
+
+    /**
+     * Test {@link LatLon#interpolate(LatLon, double)}
+     * @since 10915
+     */
+    @Test
+    public void testInterpolate() {
+        LatLon ll1 = new LatLon(0, 0);
+        LatLon ll2 = new LatLon(30, 60);
+        LatLon ll3 = new LatLon(-70, -40);
+        // lat:
+        assertEquals(15, ll1.interpolate(ll2, 0.5).lat(), 1e-10);
+        assertEquals(0, ll1.interpolate(ll2, 0).lat(), 1e-10);
+        assertEquals(30, ll1.interpolate(ll2, 1).lat(), 1e-10);
+        assertEquals(0, ll3.interpolate(ll2, .7).lat(), 1e-10);
+        // lon
+        assertEquals(30, ll1.interpolate(ll2, 0.5).lon(), 1e-10);
+        assertEquals(0, ll1.interpolate(ll2, 0).lon(), 1e-10);
+        assertEquals(60, ll1.interpolate(ll2, 1).lon(), 1e-10);
+        assertEquals(0, ll3.interpolate(ll2, .4).lon(), 1e-10);
+    }
+
+    /**
+     * Test {@link LatLon#getCenter(LatLon)}
+     * @since 10915
+     */
+    @Test
+    public void testGetCenter() {
+        LatLon ll1 = new LatLon(0, 0);
+        LatLon ll2 = new LatLon(30, 60);
+        LatLon ll3 = new LatLon(-70, -40);
+
+        assertEquals(15, ll1.getCenter(ll2).lat(), 1e-10);
+        assertEquals(15, ll2.getCenter(ll1).lat(), 1e-10);
+        assertEquals(-20, ll3.getCenter(ll2).lat(), 1e-10);
+
+        assertEquals(30, ll1.getCenter(ll2).lon(), 1e-10);
+        assertEquals(30, ll2.getCenter(ll1).lon(), 1e-10);
+        assertEquals(10, ll3.getCenter(ll2).lon(), 1e-10);
+    }
 }