package com.hankcs.hanlp.dependency.nnparser;

import com.hankcs.hanlp.corpus.io.ByteArray;
import com.hankcs.hanlp.corpus.io.ICacheAble;

import java.io.DataOutputStream;
import java.text.NumberFormat;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.util.Locale;
import java.io.PrintWriter;
import java.io.BufferedReader;
import java.io.StreamTokenizer;

/**
 * Jama = Java Matrix class.
 * <p/>
 * The Java Matrix Class provides the fundamental operations of numerical
 * linear algebra.  Various constructors create Matrices from two dimensional
 * arrays of double precision floating point numbers.  Various "gets" and
 * "sets" provide access to submatrices and matrix elements.  Several methods
 * implement basic matrix arithmetic, including matrix addition and
 * multiplication, matrix norms, and element-by-element array operations.
 * Methods for reading and printing matrices are also included.  All the
 * operations in this version of the Matrix Class involve real matrices.
 * Complex matrices may be handled in a future version.
 * <p/>
 * Five fundamental matrix decompositions, which consist of pairs or triples
 * of matrices, permutation vectors, and the like, produce results in five
 * decomposition classes.  These decompositions are accessed by the Matrix
 * class to compute solutions of simultaneous linear equations, determinants,
 * inverses and other matrix functions.  The five decompositions are:
 * <P><UL>
 * <LI>Cholesky Decomposition of symmetric, positive definite matrices.
 * <LI>LU Decomposition of rectangular matrices.
 * <LI>QR Decomposition of rectangular matrices.
 * <LI>Singular Value Decomposition of rectangular matrices.
 * <LI>Eigenvalue Decomposition of both symmetric and nonsymmetric square matrices.
 * </UL>
 * <DL>
 * <DT><B>Example of use:</B></DT>
 * <p/>
 * <DD>Solve a linear system A x = b and compute the residual norm, ||b - A x||.
 * <P><PRE>
 * double[][] vals = {{1.,2.,3},{4.,5.,6.},{7.,8.,10.}};
 * Matrix A = new Matrix(vals);
 * Matrix b = Matrix.random(3,1);
 * Matrix x = A.solve(b);
 * Matrix r = A.times(x).minus(b);
 * double rnorm = r.normInf();
 * </PRE></DD>
 * </DL>
 *
 * @author The MathWorks, Inc. and the National Institute of Standards and Technology.
 * @version 5 August 1998
 */

public class Matrix implements Cloneable, java.io.Serializable, ICacheAble
{

/* ------------------------
   Class variables
 * ------------------------ */

    /**
     * Array for internal storage of elements.
     *
     * @serial internal array storage.
     */
    private double[][] A;

    /**
     * Row and column dimensions.
     *
     * @serial row dimension.
     * @serial column dimension.
     */
    private int m, n;

/* ------------------------
   Constructors
 * ------------------------ */

    /**
     * Construct an m-by-n matrix of zeros.
     *
     * @param m Number of rows.
     * @param n Number of colums.
     */

    public Matrix(int m, int n)
    {
        this.m = m;
        this.n = n;
        A = new double[m][n];
    }

    /**
     * Construct an m-by-n constant matrix.
     *
     * @param m Number of rows.
     * @param n Number of colums.
     * @param s Fill the matrix with this scalar value.
     */

    public Matrix(int m, int n, double s)
    {
        this.m = m;
        this.n = n;
        A = new double[m][n];
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                A[i][j] = s;
            }
        }
    }

    /**
     * Construct a matrix from a 2-D array.
     *
     * @param A Two-dimensional array of doubles.
     * @throws IllegalArgumentException All rows must have the same length
     * @see #constructWithCopy
     */

    public Matrix(double[][] A)
    {
        m = A.length;
        n = A[0].length;
        for (int i = 0; i < m; i++)
        {
            if (A[i].length != n)
            {
                throw new IllegalArgumentException("All rows must have the same length.");
            }
        }
        this.A = A;
    }

    /**
     * Construct a matrix quickly without checking arguments.
     *
     * @param A Two-dimensional array of doubles.
     * @param m Number of rows.
     * @param n Number of colums.
     */

    public Matrix(double[][] A, int m, int n)
    {
        this.A = A;
        this.m = m;
        this.n = n;
    }

    /**
     * Construct a matrix from a one-dimensional packed array
     *
     * @param vals One-dimensional array of doubles, packed by columns (ala Fortran).
     * @param m    Number of rows.
     * @throws IllegalArgumentException Array length must be a multiple of m.
     */

    public Matrix(double vals[], int m)
    {
        this.m = m;
        n = (m != 0 ? vals.length / m : 0);
        if (m * n != vals.length)
        {
            throw new IllegalArgumentException("Array length must be a multiple of m.");
        }
        A = new double[m][n];
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                A[i][j] = vals[i + j * m];
            }
        }
    }

    public Matrix()
    {

    }

/* ------------------------
   Public Methods
 * ------------------------ */

    /**
     * Construct a matrix from a copy of a 2-D array.
     *
     * @param A Two-dimensional array of doubles.
     * @throws IllegalArgumentException All rows must have the same length
     */

    public static Matrix constructWithCopy(double[][] A)
    {
        int m = A.length;
        int n = A[0].length;
        Matrix X = new Matrix(m, n);
        double[][] C = X.getArray();
        for (int i = 0; i < m; i++)
        {
            if (A[i].length != n)
            {
                throw new IllegalArgumentException
                        ("All rows must have the same length.");
            }
            for (int j = 0; j < n; j++)
            {
                C[i][j] = A[i][j];
            }
        }
        return X;
    }

    /**
     * Make a deep copy of a matrix
     */

    public Matrix copy()
    {
        Matrix X = new Matrix(m, n);
        double[][] C = X.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                C[i][j] = A[i][j];
            }
        }
        return X;
    }

    /**
     * Clone the Matrix object.
     */

    public Object clone()
    {
        return this.copy();
    }

    /**
     * Access the internal two-dimensional array.
     *
     * @return Pointer to the two-dimensional array of matrix elements.
     */

    public double[][] getArray()
    {
        return A;
    }

    /**
     * Copy the internal two-dimensional array.
     *
     * @return Two-dimensional array copy of matrix elements.
     */

    public double[][] getArrayCopy()
    {
        double[][] C = new double[m][n];
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                C[i][j] = A[i][j];
            }
        }
        return C;
    }

    /**
     * Make a one-dimensional column packed copy of the internal array.
     *
     * @return Matrix elements packed in a one-dimensional array by columns.
     */

    public double[] getColumnPackedCopy()
    {
        double[] vals = new double[m * n];
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                vals[i + j * m] = A[i][j];
            }
        }
        return vals;
    }

    /**
     * Make a one-dimensional row packed copy of the internal array.
     *
     * @return Matrix elements packed in a one-dimensional array by rows.
     */

    public double[] getRowPackedCopy()
    {
        double[] vals = new double[m * n];
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                vals[i * n + j] = A[i][j];
            }
        }
        return vals;
    }

    /**
     * Get row dimension.
     *
     * @return m, the number of rows.
     */

    public int getRowDimension()
    {
        return m;
    }

    /**
     * Get column dimension.
     *
     * @return n, the number of columns.
     */

    public int getColumnDimension()
    {
        return n;
    }

    /**
     * Get a single element.
     *
     * @param i Row index.
     * @param j Column index.
     * @return A(i, j)
     * @throws ArrayIndexOutOfBoundsException
     */

    public double get(int i, int j)
    {
        return A[i][j];
    }

    /**
     * Get a submatrix.
     *
     * @param i0 Initial row index
     * @param i1 Final row index
     * @param j0 Initial column index
     * @param j1 Final column index
     * @return A(i0:i1, j0:j1)
     * @throws ArrayIndexOutOfBoundsException Submatrix indices
     */

    public Matrix getMatrix(int i0, int i1, int j0, int j1)
    {
        Matrix X = new Matrix(i1 - i0 + 1, j1 - j0 + 1);
        double[][] B = X.getArray();
        try
        {
            for (int i = i0; i <= i1; i++)
            {
                for (int j = j0; j <= j1; j++)
                {
                    B[i - i0][j - j0] = A[i][j];
                }
            }
        }
        catch (ArrayIndexOutOfBoundsException e)
        {
            throw new ArrayIndexOutOfBoundsException("Submatrix indices");
        }
        return X;
    }

    /**
     * Get a submatrix.
     *
     * @param r Array of row indices.
     * @param c Array of column indices.
     * @return A(r(:), c(:))
     * @throws ArrayIndexOutOfBoundsException Submatrix indices
     */

    public Matrix getMatrix(int[] r, int[] c)
    {
        Matrix X = new Matrix(r.length, c.length);
        double[][] B = X.getArray();
        try
        {
            for (int i = 0; i < r.length; i++)
            {
                for (int j = 0; j < c.length; j++)
                {
                    B[i][j] = A[r[i]][c[j]];
                }
            }
        }
        catch (ArrayIndexOutOfBoundsException e)
        {
            throw new ArrayIndexOutOfBoundsException("Submatrix indices");
        }
        return X;
    }

    /**
     * Get a submatrix.
     *
     * @param i0 Initial row index
     * @param i1 Final row index
     * @param c  Array of column indices.
     * @return A(i0:i1, c(:))
     * @throws ArrayIndexOutOfBoundsException Submatrix indices
     */

    public Matrix getMatrix(int i0, int i1, int[] c)
    {
        Matrix X = new Matrix(i1 - i0 + 1, c.length);
        double[][] B = X.getArray();
        try
        {
            for (int i = i0; i <= i1; i++)
            {
                for (int j = 0; j < c.length; j++)
                {
                    B[i - i0][j] = A[i][c[j]];
                }
            }
        }
        catch (ArrayIndexOutOfBoundsException e)
        {
            throw new ArrayIndexOutOfBoundsException("Submatrix indices");
        }
        return X;
    }

    /**
     * Get a submatrix.
     *
     * @param r  Array of row indices.
     * @param j0 Initial column index
     * @param j1 Final column index
     * @return A(r(:), j0:j1)
     * @throws ArrayIndexOutOfBoundsException Submatrix indices
     */

    public Matrix getMatrix(int[] r, int j0, int j1)
    {
        Matrix X = new Matrix(r.length, j1 - j0 + 1);
        double[][] B = X.getArray();
        try
        {
            for (int i = 0; i < r.length; i++)
            {
                for (int j = j0; j <= j1; j++)
                {
                    B[i][j - j0] = A[r[i]][j];
                }
            }
        }
        catch (ArrayIndexOutOfBoundsException e)
        {
            throw new ArrayIndexOutOfBoundsException("Submatrix indices");
        }
        return X;
    }

    /**
     * Set a single element.
     *
     * @param i Row index.
     * @param j Column index.
     * @param s A(i,j).
     * @throws ArrayIndexOutOfBoundsException
     */

    public void set(int i, int j, double s)
    {
        A[i][j] = s;
    }

    /**
     * Set a submatrix.
     *
     * @param i0 Initial row index
     * @param i1 Final row index
     * @param j0 Initial column index
     * @param j1 Final column index
     * @param X  A(i0:i1,j0:j1)
     * @throws ArrayIndexOutOfBoundsException Submatrix indices
     */

    public void setMatrix(int i0, int i1, int j0, int j1, Matrix X)
    {
        try
        {
            for (int i = i0; i <= i1; i++)
            {
                for (int j = j0; j <= j1; j++)
                {
                    A[i][j] = X.get(i - i0, j - j0);
                }
            }
        }
        catch (ArrayIndexOutOfBoundsException e)
        {
            throw new ArrayIndexOutOfBoundsException("Submatrix indices");
        }
    }

    /**
     * Set a submatrix.
     *
     * @param r Array of row indices.
     * @param c Array of column indices.
     * @param X A(r(:),c(:))
     * @throws ArrayIndexOutOfBoundsException Submatrix indices
     */

    public void setMatrix(int[] r, int[] c, Matrix X)
    {
        try
        {
            for (int i = 0; i < r.length; i++)
            {
                for (int j = 0; j < c.length; j++)
                {
                    A[r[i]][c[j]] = X.get(i, j);
                }
            }
        }
        catch (ArrayIndexOutOfBoundsException e)
        {
            throw new ArrayIndexOutOfBoundsException("Submatrix indices");
        }
    }

    /**
     * Set a submatrix.
     *
     * @param r  Array of row indices.
     * @param j0 Initial column index
     * @param j1 Final column index
     * @param X  A(r(:),j0:j1)
     * @throws ArrayIndexOutOfBoundsException Submatrix indices
     */

    public void setMatrix(int[] r, int j0, int j1, Matrix X)
    {
        try
        {
            for (int i = 0; i < r.length; i++)
            {
                for (int j = j0; j <= j1; j++)
                {
                    A[r[i]][j] = X.get(i, j - j0);
                }
            }
        }
        catch (ArrayIndexOutOfBoundsException e)
        {
            throw new ArrayIndexOutOfBoundsException("Submatrix indices");
        }
    }

    /**
     * Set a submatrix.
     *
     * @param i0 Initial row index
     * @param i1 Final row index
     * @param c  Array of column indices.
     * @param X  A(i0:i1,c(:))
     * @throws ArrayIndexOutOfBoundsException Submatrix indices
     */

    public void setMatrix(int i0, int i1, int[] c, Matrix X)
    {
        try
        {
            for (int i = i0; i <= i1; i++)
            {
                for (int j = 0; j < c.length; j++)
                {
                    A[i][c[j]] = X.get(i - i0, j);
                }
            }
        }
        catch (ArrayIndexOutOfBoundsException e)
        {
            throw new ArrayIndexOutOfBoundsException("Submatrix indices");
        }
    }

    /**
     * Matrix transpose.
     *
     * @return A'
     */

    public Matrix transpose()
    {
        Matrix X = new Matrix(n, m);
        double[][] C = X.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                C[j][i] = A[i][j];
            }
        }
        return X;
    }

    /**
     * One norm
     *
     * @return maximum column sum.
     */

    public double norm1()
    {
        double f = 0;
        for (int j = 0; j < n; j++)
        {
            double s = 0;
            for (int i = 0; i < m; i++)
            {
                s += Math.abs(A[i][j]);
            }
            f = Math.max(f, s);
        }
        return f;
    }

    /**
     * Infinity norm
     *
     * @return maximum row sum.
     */

    public double normInf()
    {
        double f = 0;
        for (int i = 0; i < m; i++)
        {
            double s = 0;
            for (int j = 0; j < n; j++)
            {
                s += Math.abs(A[i][j]);
            }
            f = Math.max(f, s);
        }
        return f;
    }

    /**
     * Unary minus
     *
     * @return -A
     */

    public Matrix uminus()
    {
        Matrix X = new Matrix(m, n);
        double[][] C = X.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                C[i][j] = -A[i][j];
            }
        }
        return X;
    }

    /**
     * C = A + B
     *
     * @param B another matrix
     * @return A + B
     */

    public Matrix plus(Matrix B)
    {
        checkMatrixDimensions(B);
        Matrix X = new Matrix(m, n);
        double[][] C = X.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                C[i][j] = A[i][j] + B.A[i][j];
            }
        }
        return X;
    }

    /**
     * A = A + B
     *
     * @param B another matrix
     * @return A + B
     */

    public Matrix plusEquals(Matrix B)
    {
        checkMatrixDimensions(B);
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                A[i][j] = A[i][j] + B.A[i][j];
            }
        }
        return this;
    }

    /**
     * C = A - B
     *
     * @param B another matrix
     * @return A - B
     */

    public Matrix minus(Matrix B)
    {
        checkMatrixDimensions(B);
        Matrix X = new Matrix(m, n);
        double[][] C = X.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                C[i][j] = A[i][j] - B.A[i][j];
            }
        }
        return X;
    }

    /**
     * A = A - B
     *
     * @param B another matrix
     * @return A - B
     */

    public Matrix minusEquals(Matrix B)
    {
        checkMatrixDimensions(B);
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                A[i][j] = A[i][j] - B.A[i][j];
            }
        }
        return this;
    }

    /**
     * Element-by-element multiplication, C = A.*B
     *
     * @param B another matrix
     * @return A.*B
     */

    public Matrix arrayTimes(Matrix B)
    {
        checkMatrixDimensions(B);
        Matrix X = new Matrix(m, n);
        double[][] C = X.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                C[i][j] = A[i][j] * B.A[i][j];
            }
        }
        return X;
    }

    /**
     * Element-by-element multiplication in place, A = A.*B
     *
     * @param B another matrix
     * @return A.*B
     */

    public Matrix arrayTimesEquals(Matrix B)
    {
        checkMatrixDimensions(B);
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                A[i][j] = A[i][j] * B.A[i][j];
            }
        }
        return this;
    }

    /**
     * Element-by-element right division, C = A./B
     *
     * @param B another matrix
     * @return A./B
     */

    public Matrix arrayRightDivide(Matrix B)
    {
        checkMatrixDimensions(B);
        Matrix X = new Matrix(m, n);
        double[][] C = X.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                C[i][j] = A[i][j] / B.A[i][j];
            }
        }
        return X;
    }

    /**
     * Element-by-element right division in place, A = A./B
     *
     * @param B another matrix
     * @return A./B
     */

    public Matrix arrayRightDivideEquals(Matrix B)
    {
        checkMatrixDimensions(B);
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                A[i][j] = A[i][j] / B.A[i][j];
            }
        }
        return this;
    }

    /**
     * Element-by-element left division, C = A.\B
     *
     * @param B another matrix
     * @return A.\B
     */

    public Matrix arrayLeftDivide(Matrix B)
    {
        checkMatrixDimensions(B);
        Matrix X = new Matrix(m, n);
        double[][] C = X.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                C[i][j] = B.A[i][j] / A[i][j];
            }
        }
        return X;
    }

    /**
     * Element-by-element left division in place, A = A.\B
     *
     * @param B another matrix
     * @return A.\B
     */

    public Matrix arrayLeftDivideEquals(Matrix B)
    {
        checkMatrixDimensions(B);
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                A[i][j] = B.A[i][j] / A[i][j];
            }
        }
        return this;
    }

    /**
     * Multiply a matrix by a scalar, C = s*A
     *
     * @param s scalar
     * @return s*A
     */

    public Matrix times(double s)
    {
        Matrix X = new Matrix(m, n);
        double[][] C = X.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                C[i][j] = s * A[i][j];
            }
        }
        return X;
    }

    /**
     * Multiply a matrix by a scalar in place, A = s*A
     *
     * @param s scalar
     * @return replace A by s*A
     */

    public Matrix timesEquals(double s)
    {
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                A[i][j] = s * A[i][j];
            }
        }
        return this;
    }

    /**
     * Linear algebraic matrix multiplication, A * B
     *
     * @param B another matrix
     * @return Matrix product, A * B
     * @throws IllegalArgumentException Matrix inner dimensions must agree.
     */

    public Matrix times(Matrix B)
    {
        if (B.m != n)
        {
            throw new IllegalArgumentException("Matrix inner dimensions must agree.");
        }
        Matrix X = new Matrix(m, B.n);
        double[][] C = X.getArray();
        double[] Bcolj = new double[n];
        for (int j = 0; j < B.n; j++)
        {
            for (int k = 0; k < n; k++)
            {
                Bcolj[k] = B.A[k][j];
            }
            for (int i = 0; i < m; i++)
            {
                double[] Arowi = A[i];
                double s = 0;
                for (int k = 0; k < n; k++)
                {
                    s += Arowi[k] * Bcolj[k];
                }
                C[i][j] = s;
            }
        }
        return X;
    }


    /**
     * Matrix trace.
     *
     * @return sum of the diagonal elements.
     */

    public double trace()
    {
        double t = 0;
        for (int i = 0; i < Math.min(m, n); i++)
        {
            t += A[i][i];
        }
        return t;
    }

    /**
     * Generate matrix with random elements
     *
     * @param m Number of rows.
     * @param n Number of colums.
     * @return An m-by-n matrix with uniformly distributed random elements.
     */

    public static Matrix random(int m, int n)
    {
        Matrix A = new Matrix(m, n);
        double[][] X = A.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                X[i][j] = Math.random();
            }
        }
        return A;
    }

    /**
     * Generate identity matrix
     *
     * @param m Number of rows.
     * @param n Number of colums.
     * @return An m-by-n matrix with ones on the diagonal and zeros elsewhere.
     */

    public static Matrix identity(int m, int n)
    {
        Matrix A = new Matrix(m, n);
        double[][] X = A.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                X[i][j] = (i == j ? 1.0 : 0.0);
            }
        }
        return A;
    }


    /**
     * Print the matrix to stdout.   Line the elements up in columns
     * with a Fortran-like 'Fw.d' style format.
     *
     * @param w Column width.
     * @param d Number of digits after the decimal.
     */

    public void print(int w, int d)
    {
        print(new PrintWriter(System.out, true), w, d);
    }

    /**
     * Print the matrix to the output stream.   Line the elements up in
     * columns with a Fortran-like 'Fw.d' style format.
     *
     * @param output Output stream.
     * @param w      Column width.
     * @param d      Number of digits after the decimal.
     */

    public void print(PrintWriter output, int w, int d)
    {
        DecimalFormat format = new DecimalFormat();
        format.setDecimalFormatSymbols(new DecimalFormatSymbols(Locale.US));
        format.setMinimumIntegerDigits(1);
        format.setMaximumFractionDigits(d);
        format.setMinimumFractionDigits(d);
        format.setGroupingUsed(false);
        print(output, format, w + 2);
    }

    /**
     * Print the matrix to stdout.  Line the elements up in columns.
     * Use the format object, and right justify within columns of width
     * characters.
     * Note that is the matrix is to be read back in, you probably will want
     * to use a NumberFormat that is set to US Locale.
     *
     * @param format A  Formatting object for individual elements.
     * @param width  Field width for each column.
     * @see DecimalFormat#setDecimalFormatSymbols
     */

    public void print(NumberFormat format, int width)
    {
        print(new PrintWriter(System.out, true), format, width);
    }

    // DecimalFormat is a little disappointing coming from Fortran or C's printf.
    // Since it doesn't pad on the left, the elements will come out different
    // widths.  Consequently, we'll pass the desired column width in as an
    // argument and do the extra padding ourselves.

    /**
     * Print the matrix to the output stream.  Line the elements up in columns.
     * Use the format object, and right justify within columns of width
     * characters.
     * Note that is the matrix is to be read back in, you probably will want
     * to use a NumberFormat that is set to US Locale.
     *
     * @param output the output stream.
     * @param format A formatting object to format the matrix elements
     * @param width  Column width.
     * @see DecimalFormat#setDecimalFormatSymbols
     */

    public void print(PrintWriter output, NumberFormat format, int width)
    {
        output.println();  // start on new line.
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                String s = format.format(A[i][j]); // format the number
                int padding = Math.max(1, width - s.length()); // At _least_ 1 space
                for (int k = 0; k < padding; k++)
                    output.print(' ');
                output.print(s);
            }
            output.println();
        }
        output.println();   // end with blank line.
    }

    /**
     * Read a matrix from a stream.  The format is the same the print method,
     * so printed matrices can be read back in (provided they were printed using
     * US Locale).  Elements are separated by
     * whitespace, all the elements for each row appear on a single line,
     * the last row is followed by a blank line.
     *
     * @param input the input stream.
     */

    public static Matrix read(BufferedReader input) throws java.io.IOException
    {
        StreamTokenizer tokenizer = new StreamTokenizer(input);

        // Although StreamTokenizer will parse numbers, it doesn't recognize
        // scientific notation (E or D); however, Double.valueOf does.
        // The strategy here is to disable StreamTokenizer's number parsing.
        // We'll only get whitespace delimited words, EOL's and EOF's.
        // These words should all be numbers, for Double.valueOf to parse.

        tokenizer.resetSyntax();
        tokenizer.wordChars(0, 255);
        tokenizer.whitespaceChars(0, ' ');
        tokenizer.eolIsSignificant(true);
        java.util.Vector<Double> vD = new java.util.Vector<Double>();

        // Ignore initial empty lines
        while (tokenizer.nextToken() == StreamTokenizer.TT_EOL) ;
        if (tokenizer.ttype == StreamTokenizer.TT_EOF)
            throw new java.io.IOException("Unexpected EOF on matrix read.");
        do
        {
            vD.addElement(Double.valueOf(tokenizer.sval)); // Read & store 1st row.
        }
        while (tokenizer.nextToken() == StreamTokenizer.TT_WORD);

        int n = vD.size();  // Now we've got the number of columns!
        double row[] = new double[n];
        for (int j = 0; j < n; j++)  // extract the elements of the 1st row.
            row[j] = vD.elementAt(j).doubleValue();
        java.util.Vector<double[]> v = new java.util.Vector<double[]>();
        v.addElement(row);  // Start storing rows instead of columns.
        while (tokenizer.nextToken() == StreamTokenizer.TT_WORD)
        {
            // While non-empty lines
            v.addElement(row = new double[n]);
            int j = 0;
            do
            {
                if (j >= n) throw new java.io.IOException
                        ("Row " + v.size() + " is too long.");
                row[j++] = Double.valueOf(tokenizer.sval).doubleValue();
            }
            while (tokenizer.nextToken() == StreamTokenizer.TT_WORD);
            if (j < n) throw new java.io.IOException
                    ("Row " + v.size() + " is too short.");
        }
        int m = v.size();  // Now we've got the number of rows.
        double[][] A = new double[m][];
        v.copyInto(A);  // copy the rows out of the vector
        return new Matrix(A);
    }


/* ------------------------
   Private Methods
 * ------------------------ */

    /**
     * Check if size(A) == size(B)
     **/

    private void checkMatrixDimensions(Matrix B)
    {
        if (B.m != m || B.n != n)
        {
            throw new IllegalArgumentException("Matrix dimensions must agree.");
        }
    }

    private static final long serialVersionUID = 1;

    public static Matrix zero(int m, int n)
    {
        Matrix A = new Matrix(m, n);
        double[][] X = A.getArray();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                X[i][j] = 0.0;
            }
        }
        return A;
    }

    public int rows()
    {
        return getRowDimension();
    }

    public int cols()
    {
        return getColumnDimension();
    }

    /**
     * 取出第j列作为一个列向量
     * @param j
     * @return
     */
    public Matrix col(int j)
    {
        double[][] X = new double[m][1];
        for (int i = 0; i < m; i++)
        {
            X[i][0] = A[i][j];
        }
        return new Matrix(X);
    }

    /**
     * 取出第i行作为一个行向量
     * @param i
     * @return
     */
    public Matrix row(int i)
    {
        double[][] X = new double[1][n];
        for (int j = 0; j < n; j++)
        {
            X[0][j] = A[i][j];
        }
        return new Matrix(X);
    }

    public Matrix block(int i, int j, int p, int q)
    {
        return getMatrix(i, i + p - 1, j, j + q - 1);
    }

    /**
     * 返回矩阵的立方(以数组形式)
     * @return
     */
    public double[][] cube()
    {
        double[][] X = new double[m][n];
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                X[i][j] = Math.pow(A[i][j], 3.);
            }
        }

        return X;
    }

    public void setZero()
    {
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                A[i][j] = 0.;
            }
        }
    }

    public void save(DataOutputStream out) throws Exception
    {
        out.writeInt(m);
        out.writeInt(n);
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                out.writeDouble(A[i][j]);
            }
        }
    }

    public boolean load(ByteArray byteArray)
    {
        m = byteArray.nextInt();
        n = byteArray.nextInt();
        A = new double[m][n];
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                A[i][j] = byteArray.nextDouble();
            }
        }
        return true;
    }
}