package com.imsl.test.example.math;

import com.imsl.math.*;
import java.io.*;

/**
 * <p>
 * SparseMatrix Example 2: Converts a matrix in market format to a sparse matrix
 * format.
 * </p>
 * The matrix market exchange format is an ASCII file format that represents
 * sparse matrices in coordinate format. It consists of three sections: The
 * header section is the first line in the file and contains general information
 * about the matrix, e.g. data type and symmetry properties. This line is
 * followed by the comments section which consists of zero or more lines of
 * comments. The remainder of the file is the data section. The first line of
 * the data section contains the row number, column number, and number of
 * nonzeros of the matrix. The following lines contain the location and value of
 * all nonzero entries of the matrix, usually one per line. A file in Matrix
 * Market format is read and converted to a JMSL SparseMatrix in this example.
 * Matrix information and the one norm of the matrix are printed.
 *
 * @see <a href="SparseMatrixEx2.java">Code</a>
 * @see <a href="doc-files/SparseMatrixEx2.out">Output</a>
 */
public class SparseMatrixEx2 {

    /**
     * Reads a file containing Market format data.
     */
    public static class MTXReader {

        private String typecode;
        private SparseMatrix matrix;

        /**
         * Reads a file.
         *
         * @param filename a <code>String</code>, the name of the file
         * @throws java.io.IOException
         */
        public void read(String filename) throws java.io.IOException {
            try (InputStream s = SparseMatrixEx2.class.getResourceAsStream(filename)) {
                BufferedReader br = new BufferedReader(new InputStreamReader(s));

                // read type code initial line
                String line = br.readLine();
                typecode = line;

                // read comment lines if any
                boolean comment = true;
                while (comment) {
                    line = br.readLine();
                    comment = line.startsWith("%");
                }

                // line now contains the size information which needs to be parsed
                String[] str = line.split("( )+");
                int nRows = Integer.valueOf(str[0].trim());
                int nColumns = Integer.valueOf(str[1].trim());

                // now we're into the data section
                matrix = new SparseMatrix(nRows, nColumns);
                while (true) {
                    line = br.readLine();
                    if (line == null) {
                        break;
                    }
                    str = line.split("( )+");
                    int i = Integer.valueOf(str[0].trim());
                    int j = Integer.valueOf(str[1].trim());
                    double x = Double.valueOf(str[2].trim());
                    matrix.set(i - 1, j - 1, x);
                }
                br.close();
            }
        }

        public String getTypeCode() {
            return this.typecode;
        }
    }

    public static void main(String args[]) throws Exception {
        MTXReader mr = new MTXReader();
        mr.read("bcsstk01.mtx");
        SparseMatrix A = mr.matrix;

        // Print the matrix type
        System.out.println("The matrix type is " + mr.getTypeCode());

        // Print the matrix information and its one norm
        System.out.println("The number of rows is " + A.getNumberOfRows());
        int ncols = A.getNumberOfColumns();
        System.out.println("The number of columns is " + ncols);
        long nnz = A.getNumberOfNonZeros();
        System.out.println("The number of nonzero elements is " + nnz);
        System.out.println();
        System.out.println("The 1 norm of the matrix is " + A.oneNorm());
    }
}