import cern.colt.matrix.tfloat.FloatMatrix2D;
   import cern.colt.matrix.tfloat.algo.DenseFloatAlgebra;
   import cern.colt.matrix.tfloat.algo.SparseFloatAlgebra;
   import cern.colt.matrix.tfloat.algo.decomposition.DenseFloatLUDecomposition;
   import cern.colt.matrix.tfloat.algo.decomposition.SparseFloatLUDecomposition;
   import cern.colt.matrix.tfloat.impl.DenseFloatMatrix2D;
   import cern.colt.matrix.tfloat.impl.SparseCCFloatMatrix2D;
   
   /**
   * Demonstrate the determinant has wrong sign problem.
   * <p>
   * Copyright (c) 2013-2015 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="http://opentrafficsim.org/docs/license.html">OpenTrafficSim License</a>.
   * <p>
   * $LastChangedDate: 2015-08-30 00:16:51 +0200 (Sun, 30 Aug 2015) $, @version $Revision: 1329 $, by $Author: averbraeck $,
   * initial version mrt. 2015 <br>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   */
  public final class DeterminantProblem
  {
      /**
       * This class should never be instantiated.
       */
      private DeterminantProblem()
      {
          // This class should never be instantiated.
      }
  
      /**
       * Execute the demo.
       * @param args String[]; not used
       */
      public static void main(final String[] args)
      {
          float[][] values = {{1, 2, 3}, {3, 5, 7}, {5, 10, 0}};
  
          FloatMatrix2D sparseFloatMatrix2D = new SparseCCFloatMatrix2D(values.length, values[0].length);
          FloatMatrix2D denseFloatMatrix2D = new DenseFloatMatrix2D(values.length, values[0].length);
  
          for (int row = 0; row < values.length; row++)
          {
              for (int column = 0; column < values[row].length; column++)
              {
                  sparseFloatMatrix2D.set(row, column, values[row][column]);
                  denseFloatMatrix2D.set(row, column, values[row][column]);
              }
          }
          System.out.println("sparse matrix: " + sparseFloatMatrix2D.toString());
          float sparseDeterminant = new SparseFloatAlgebra().det(sparseFloatMatrix2D);
          System.out.println("determinant returned by det() is " + sparseDeterminant
              + " (prints -15.0; correct value is 15.0)");
          System.out.println("");
          System.out.println("dense matrix: " + denseFloatMatrix2D.toString());
          float denseDeterminant = new DenseFloatAlgebra().det(denseFloatMatrix2D);
          System.out.println("determinant returned by det() is " + denseDeterminant + " (prints 15.0 which is OK)");
  
          System.out.println("");
          System.out.println("The L and U matrices of the LU decompositions look fine and are identical (except for "
              + "one being sparse and the other dense).");
          SparseFloatLUDecomposition sparseLU = new SparseFloatLUDecomposition(sparseFloatMatrix2D, 0, true);
          DenseFloatLUDecomposition denseLU = new DenseFloatLUDecomposition(denseFloatMatrix2D);
  
          System.out.println("sparse L: " + sparseLU.getL());
          System.out.println("dense L: " + denseLU.getL());
          System.out.println("");
          System.out.println("sparse U: " + sparseLU.getU());
          System.out.println("dense U: " + denseLU.getU());
  
          sparseLU.det();
          denseLU.det();
      }
  
  }