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/*
 * Copyright 1998-2009 University Corporation for Atmospheric Research/Unidata
 *
 * Portions of this software were developed by the Unidata Program at the
 * University Corporation for Atmospheric Research.
 *
 * Access and use of this software shall impose the following obligations
 * and understandings on the user. The user is granted the right, without
 * any fee or cost, to use, copy, modify, alter, enhance and distribute
 * this software, and any derivative works thereof, and its supporting
 * documentation for any purpose whatsoever, provided that this entire
 * notice appears in all copies of the software, derivative works and
 * supporting documentation.  Further, UCAR requests that the user credit
 * UCAR/Unidata in any publications that result from the use of this
 * software or in any product that includes this software. The names UCAR
 * and/or Unidata, however, may not be used in any advertising or publicity
 * to endorse or promote any products or commercial entity unless specific
 * written permission is obtained from UCAR/Unidata. The user also
 * understands that UCAR/Unidata is not obligated to provide the user with
 * any support, consulting, training or assistance of any kind with regard
 * to the use, operation and performance of this software nor to provide
 * the user with any updates, revisions, new versions or "bug fixes."
 *
 * THIS SOFTWARE IS PROVIDED BY UCAR/UNIDATA "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL UCAR/UNIDATA BE LIABLE FOR ANY SPECIAL,
 * INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
 * FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
 * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 * WITH THE ACCESS, USE OR PERFORMANCE OF THIS SOFTWARE.
 */

package ucar.ma2;

/**
 * Abstraction for matrix operations.
 * A matrix is a rank-2 Array: m[rows, cols].
 * All operations done in double precision (??)
 *
 * @author @caron
 */

public class MAMatrix {
  private Array a;
  private int nrows, ncols;
  private Index ima;

  /**
   * Create an MAMatrix of the given shape.
   * @param nrows number of rows
   * @param ncols number of cols
   */
  public MAMatrix( int nrows, int ncols) {
    this.a = new ArrayDouble.D2(nrows, ncols);
    this.nrows = nrows;
    this.ncols = ncols;
    ima = a.getIndex();
  }
  /**
   * Create an MAMatrix using the given rank-2 array.
   * @param a rank-2 array
   * @exception IllegalArgumentException is a is not rank 2
   */
  public MAMatrix( Array a) {
    this.a = a;
    if (a.getRank() != 2)
      throw new IllegalArgumentException("rank != 2, instead = "+ a.getRank());
    nrows = a.getShape()[0];
    ncols = a.getShape()[1];
    ima = a.getIndex();
  }

  public int getNrows() { return nrows; }
  public int getNcols() { return ncols; }
  public double getDouble(int i, int j) { return a.getDouble(ima.set(i,j)); }
  public void setDouble(int i, int j, double val) { a.setDouble(ima.set(i,j), val); }

  /**
   * Create a new MAMatrix that is the same as this one, with a copy of the backing store.
   */
  public MAMatrix copy() {
    return new MAMatrix( a.copy());
  }

  /**
   * Create a MAMatrix that is the transpose of this one, with the same backing store.
   * Use copy() to get a copy.
   */
  public MAMatrix transpose() {
    return new MAMatrix( a.transpose(0,1));
  }

  /**
   * Get the jth column, return as a MAVector: same backing store.
   */
  public MAVector column(int j) {
    return new MAVector( a.slice(1,j));
  }

  /**
   * Get the ith row, return as a MAVector: same backing store.
   */
  public MAVector row(int i) {
    return new MAVector( a.slice(0,i));
  }

  /**
   * Dot product of matrix and vector: return M dot v
   * @param v dot product with this vector
   * @return MAVector result: new vector
   * @exception IllegalArgumentException if ncols != v.getSize().
   */
  public MAVector dot(MAVector v) {

    if (ncols != v.getNelems())
      throw new IllegalArgumentException("MAMatrix.dot "+ncols+" != "+ v.getNelems());

    ArrayDouble.D1 result = new ArrayDouble.D1(nrows);
    Index imr = result.getIndex();

    for (int i=0; i