/*

     This file is part of Combean.

     Combean is free software; you can redistribute it and/or modify

     it under the terms of the GNU General Public License as published by

     the Free Software Foundation; either version 2 of the License, or

     (at your option) any later version.

     Combean 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 General Public License for more details.

     You should have received a copy of the GNU General Public License

     along with Combean; if not, write to the Free Software

     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 */

 /*

  * Created on 22.04.2005

  *

  */

 package net.sourceforge.combean.mathprog.linalg.statics;

 import net.sourceforge.combean.interfaces.mathprog.linalg.SparseVec;

 import net.sourceforge.combean.interfaces.mathprog.linalg.SparseVector;

 import net.sourceforge.combean.interfaces.mathprog.linalg.VectorIterator;

 import net.sourceforge.combean.interfaces.mathprog.linalg.VectorValue;

 import net.sourceforge.combean.interfaces.mathprog.lp.model.NoLabel;

 /**

  * Collection of static helper functions to convert SparseVectors to

  * plain Java arrays.

  * 

  * @author schickin

  *

  */

 public final class SparseVectorConverter {

     /**

      * Convert a sparse vector given by an iterator over its components

      * to a plain double array

      * 

      * @param dim the dimension of the dense output double array

      * @param itVec the iterator over the entries in the sparse vector

      * @return the entries represented by itVec as double array

      */

     public static double[] convertToDoubleArray(int dim,

             VectorIterator<NoLabel> itVec) {

         double[] result = new double[dim];

         for (int i = 0; i < dim; i++) {

             result[i] = 0;

         }

         while (itVec.hasNext()) {

             VectorValue<NoLabel> currValue = itVec.next();

             result[currValue.index()] = currValue.doubleValue();

         }

         return result;

     }

     /**

      * Convert SparseVec to plain double array

      * 

      * @param dim desired dimension of the output array. must be big

      * enough such that all entries in vec fit into the output

      * @param vec the vector to be converted

      * @return vec as double array

      */

     public static double[] convertToDoubleArray(int dim,

             SparseVec<NoLabel> vec) {

         return convertToDoubleArray(dim, vec.iterator());

     }

     /**

      * Convert SparseVec to plain double array, giving the double array the exact dimension of the

      * sparse vector.

      * 

      * @param vec the vector to be converted

      * @return vec as double array

      */

     public static double[] convertToDoubleArray(

             SparseVector vec) {

         return convertToDoubleArray(vec.getDimension(), vec);

     }

     /**

      * Convert an SparseVec to two plain Java arrays, one containing the

      * indices of non-zero entries and a double array containing their

      * values.

      * 

      * @param vec the vector to be converted

      * @param indexArr the index array to be filled. must be large enough

      * to accomodate all entries of vec.

      * @param valueArr the value array to be filled. must be large enough

      * to accomodate all entries of vec.

      */

     public static <T> void convertToIndexAndDoubleArray(SparseVec<T> vec,

             int[] indexArr, double[] valueArr) {

         int currIdx = 0;

         T label = null;

         VectorIterator<T> itVec = vec.iterator();

         while (itVec.hasNext()) {

             VectorValue<T> currValue = itVec.next();

             if (label == null) {

                 label = currValue.label();

             }

             else {

                 assert label == currValue.label();

             }

             indexArr[currIdx] = currValue.index();

             valueArr[currIdx] = currValue.doubleValue();

             currIdx++;

         }

     }

 }