1 files changed, 91 insertions, 0 deletions
diff --git a/src/de/lmu/ifi/dbs/elki/index/tree/spatial/rstarvariants/strategies/bulk/AbstractBulkSplit.java b/src/de/lmu/ifi/dbs/elki/index/tree/spatial/rstarvariants/strategies/bulk/AbstractBulkSplit.java
new file mode 100644
index 00000000..4a0304f1
--- /dev/null
+++ b/src/de/lmu/ifi/dbs/elki/index/tree/spatial/rstarvariants/strategies/bulk/AbstractBulkSplit.java
@@ -0,0 +1,91 @@
+package de.lmu.ifi.dbs.elki.index.tree.spatial.rstarvariants.strategies.bulk;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/*
+ 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/>.
+ */
+
+/**
+ * Encapsulates the required parameters for a bulk split of a spatial index.
+ * 
+ * @author Elke Achtert
+ */
+public abstract class AbstractBulkSplit implements BulkSplit {
+  /**
+   * Constructor
+   */
+  public AbstractBulkSplit() {
+    // Nothing to do
+  }
+
+  /**
+   * Computes and returns the best split point.
+   * 
+   * @param numEntries the number of entries to be split
+   * @param minEntries the number of minimum entries in the node to be split
+   * @param maxEntries number of maximum entries in the node to be split
+   * @return the best split point
+   */
+  protected int chooseBulkSplitPoint(int numEntries, int minEntries, int maxEntries) {
+    if(numEntries < minEntries) {
+      throw new IllegalArgumentException("numEntries < minEntries!");
+    }
+
+    if(numEntries <= maxEntries) {
+      return numEntries;
+    }
+    else if(numEntries < maxEntries + minEntries) {
+      return (numEntries - minEntries);
+    }
+    else {
+      return maxEntries;
+    }
+  }
+
+  /**
+   * Perform the trivial partitioning of the given list.
+   * 
+   * @param objects Objects to partition
+   * @param minEntries Minimum number of objects per page
+   * @param maxEntries Maximum number of objects per page.
+   * @return List with partitions
+   */
+  protected <T> List<List<T>> trivialPartition(List<T> objects, int minEntries, int maxEntries) {
+    // build partitions
+    final int size = objects.size();
+    final int numberPartitions = (int) Math.ceil(((double) size) / maxEntries);
+    List<List<T>> partitions = new ArrayList<List<T>>(numberPartitions);
+    int start = 0;
+    for(int pnum = 0; pnum < numberPartitions; pnum++) {
+      int end = (int) ((pnum + 1.) * size / numberPartitions);
+      if(pnum == numberPartitions - 1) {
+        end = size;
+      }
+      assert ((end - start) >= minEntries && (end - start) <= maxEntries);
+      partitions.add(objects.subList(start, end));
+      start = end;
+    }
+    return partitions;
+  }
+}
+\ No newline at end of file