--- a/flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/BackJumpCorrector.java	Fri May 27 10:09:46 2011 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/BackJumpCorrector.java	Fri May 27 16:52:37 2011 +0000
@@ -38,41 +38,33 @@
         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;
-            }
+    public boolean doCorrection(double [] km, double [] ws) {
+
+        boolean wsUp = isIncreasing(ws);
+
+        if (wsUp) {
+            km = swapClone(km);
+            ws = swapClone(ws);
         }
-        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 kmUp = isIncreasing(km);
+
+        if (!kmUp) {
+            km = sumDiffs(km);
+        }
+
+        if (log.isDebugEnabled()) {
+            log.debug("BackJumpCorrector.doCorrection ------- enter");
+            log.debug("  km increasing: " + isIncreasing(km));
+            log.debug("  ws increasing: " + isIncreasing(ws));
+            log.debug("BackJumpCorrector.doCorrection ------- leave");
         }
 
         boolean hasBackJumps = doCorrectionClean(km, ws);
 
-        if (hasBackJumps && isIncreasing) {
+        if (hasBackJumps && wsUp) {
             // mirror back
-            for (int i = 0; i < corrected.length; ++i) {
-                corrected[i] = -corrected[i];
-            }
+            swap(corrected);
         }
 
         return hasBackJumps;
@@ -134,7 +126,7 @@
             }
 
             if (back < 0) {
-                log.debug("run over left border");
+                //log.debug("run over left border");
                 // fill with same as ws[i]
                 for (int j = 0; j < i; ++j) {
                     ws[j] = ws[i];
@@ -195,6 +187,12 @@
                 interpolator = new SplineInterpolator();
             }
 
+            if (log.isDebugEnabled()) {
+                for (int j = 0; j < x.length; ++j) {
+                    log.debug("   " + x[j] + " -> " + y[j]);
+                }
+            }
+
             PolynomialSplineFunction spline = interpolator.interpolate(x, y);
 
             try {
@@ -224,5 +222,64 @@
 
         return !backjumps.isEmpty();
     }
+
+    public static final boolean isIncreasing(double [] array) {
+        int inc = 0;
+        int dec = 0;
+        int sweet = (array.length-1)/2;
+        for (int i = 1; i < array.length; ++i) {
+            if (array[i] > array[i-1]) {
+                if (++inc > sweet) {
+                    return true;
+                }
+            }
+            else if (++dec > sweet) {
+                return false;
+            }
+        }
+        return inc > sweet;
+    }
+
+    public static final double [] swap(double [] array) {
+        int lo = 0;
+        int hi = array.length-1;
+        while (hi > lo) {
+            double t  = array[lo];
+            array[lo] = array[hi];
+            array[hi] = t;
+            ++lo;
+            --hi;
+        }
+
+        return array;
+    }
+
+    public static final double [] swapClone(double [] array) {
+        double [] out = new double[array.length];
+        int lo = 0;
+
+        int hi = array.length-1;
+        while (hi > lo) {
+            out[lo] = array[hi];
+            out[hi] = array[lo];
+            ++lo;
+            --hi;
+        }
+        return out;
+    }
+
+    public static final double [] sumDiffs(double [] in) {
+        double [] out = new double[in.length];
+
+        if (out.length > 0) {
+            out[0] = 0d;
+        }
+
+        for (int i = 1; i < out.length; ++i) {
+            out[i] = out[i-1] + Math.abs(in[i-1] - in[i]);
+        }
+
+        return out;
+    }
 }
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