1 files changed, 91 insertions, 0 deletions
diff --git a/src/de/lmu/ifi/dbs/elki/math/spacefillingcurves/ZCurveSpatialSorter.java b/src/de/lmu/ifi/dbs/elki/math/spacefillingcurves/ZCurveSpatialSorter.java
new file mode 100644
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--- /dev/null
+++ b/src/de/lmu/ifi/dbs/elki/math/spacefillingcurves/ZCurveSpatialSorter.java
@@ -0,0 +1,91 @@
+package de.lmu.ifi.dbs.elki.math.spacefillingcurves;
+
+/*
+ This file is part of ELKI:
+ Environment for Developing KDD-Applications Supported by Index-Structures
+
+ Copyright (C) 2012
+ Ludwig-Maximilians-Universität München
+ Lehr- und Forschungseinheit für Datenbanksysteme
+ ELKI Development Team
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Affero General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU Affero General Public License for more details.
+
+ You should have received a copy of the GNU Affero General Public License
+ along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+import java.util.List;
+
+import de.lmu.ifi.dbs.elki.data.spatial.SpatialComparable;
+
+/**
+ * Class to sort the data set by their Z-index, without doing a full
+ * materialization of the Z indexes.
+ * 
+ * @author Erich Schubert
+ */
+public class ZCurveSpatialSorter extends AbstractSpatialSorter {
+  private static final double STOPVAL = 1E-10;
+
+  @Override
+  public <T extends SpatialComparable> void sort(List<T> objs, int start, int end, double[] minmax) {
+    zSort(objs, start, end, minmax, 0);
+  }
+
+  /**
+   * The actual Z sorting function
+   * 
+   * @param objs Objects to sort
+   * @param start Start
+   * @param end End
+   * @param mms Min-Max value ranges
+   * @param dim Current dimension
+   */
+  protected <T extends SpatialComparable> void zSort(List<T> objs, int start, int end, double[] mms, int dim) {
+    // Find the splitting points.
+    final double min = mms[2 * dim], max = mms[2 * dim + 1];
+    double spos = (min + max) / 2.;
+    // Safeguard against duplicate points:
+    if(max - spos < STOPVAL || spos - min < STOPVAL) {
+      boolean ok = false;
+      for(int d = 0; d < mms.length; d += 2) {
+        if(mms[d + 1] - mms[d] >= STOPVAL) {
+          // LoggingUtil.warning("No: " + (mms[d + 1] - mms[d]));
+          ok = true;
+          break;
+        }
+      }
+      if(!ok) {
+        return;
+      }
+    }
+    int split = pivotizeList1D(objs, start, end, dim + 1, spos, false);
+    assert (start <= split && split <= end);
+    int nextdim = (dim + 1) % objs.get(0).getDimensionality();
+    // LoggingUtil.warning("dim: " + dim + " min: " + min + " split: " + spos +
+    // " max:" + max + " " + start + " < " + split + " < " + end);
+    if(start < split - 1) {
+      mms[2 * dim] = min;
+      mms[2 * dim + 1] = spos;
+      zSort(objs, start, split, mms, nextdim);
+    }
+    if(split < end - 1) {
+      mms[2 * dim] = spos;
+      mms[2 * dim + 1] = max;
+      zSort(objs, split, end, mms, nextdim);
+    }
+    // Restore ranges
+    mms[2 * dim] = min;
+    mms[2 * dim + 1] = max;
+    // FIXME: implement completely and test.
+  }
+}
+\ No newline at end of file