# HG changeset patch
# User Sascha L. Teichmann <sascha.teichmann@intevation.de>
# Date 1304804042 0
# Node ID 663aa18bee7fa6e13602960161ab58cb22fb487f
# Parent  55c2b0d9999e1f65da82b1381b4166a451ff8d63
Back jump correction should work now for both flow directions.


flys-artifacts/trunk@1848 c6561f87-3c4e-4783-a992-168aeb5c3f6f

diff -r 55c2b0d9999e -r 663aa18bee7f flys-artifacts/ChangeLog
--- a/flys-artifacts/ChangeLog	Fri May 06 16:49:31 2011 +0000
+++ b/flys-artifacts/ChangeLog	Sat May 07 21:34:02 2011 +0000
@@ -1,3 +1,9 @@
+2011-05-07	Sascha L. Teichmann	<sascha.teichmann@intevation.de>
+
+	* src/main/java/de/intevation/flys/artifacts/math/BackJumpCorrector.java:
+	  Added code to make back jump correction work with both
+	  potential flow directions.
+
 2011-05-06	Sascha L. Teichmann	<sascha.teichmann@intevation.de>
 
 	* src/main/resources/metadata/template.xml:
diff -r 55c2b0d9999e -r 663aa18bee7f flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/BackJumpCorrector.java
--- a/flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/BackJumpCorrector.java	Fri May 06 16:49:31 2011 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/BackJumpCorrector.java	Sat May 07 21:34:02 2011 +0000
@@ -38,7 +38,47 @@
         return corrected;
     }
 
+    private static final boolean isIncreasing(double [] ws) {
+        int inc = 0;
+        int dec = 0;
+        int sweet = (ws.length-1)/2;
+        for (int i = 1; i < ws.length; ++i) {
+            if (ws[i] > ws[i-1]) {
+                if (++inc > sweet) {
+                    return true;
+                }
+            }
+            else if (++dec > sweet) {
+                return false;
+            }
+        }
+        return inc > sweet;
+    }
+
     public boolean doCorrection(double [] km, double [] ws) {
+        boolean isIncreasing = isIncreasing(ws);
+
+        if (isIncreasing) {
+            // mirror along x axis to simulate decreasing values
+            ws = (double [])ws.clone();
+            for (int i = 0; i < ws.length; ++i) {
+                ws[i] = -ws[i];
+            }
+        }
+
+        boolean hasBackJumps = doCorrectionClean(km, ws);
+
+        if (hasBackJumps && isIncreasing) {
+            // mirror back
+            for (int i = 0; i < corrected.length; ++i) {
+                corrected[i] = -corrected[i];
+            }
+        }
+
+        return hasBackJumps;
+    }
+
+    protected boolean doCorrectionClean(double [] km, double [] ws) {
         int N = km.length;
 
         if (N != ws.length) {