Example usage for org.apache.commons.math.linear RealMatrix solve

Introduction

In this page you can find the example usage for org.apache.commons.math.linear RealMatrix solve.

Prototype

@Deprecated
RealMatrix solve(RealMatrix b) throws IllegalArgumentException, InvalidMatrixException;

Source Link

Document

Returns a matrix of (column) solution vectors for linear systems with coefficient matrix = this and constant vectors = columns of b.

Usage

From source file:com.discursive.jccook.math.SolveEquations.java

public static void main(String[] args) {

    double[][] coefficients = { { 3.0, 20.0, 89.0 }, { 4.0, 40.0, 298.0 }, { 7.0, 21.0, 0.42 } };

    double[] values = { 1324, 2999, 2039 };

    RealMatrix matrix = new RealMatrixImpl(coefficients);

    double[] answers = matrix.solve(values);

    System.out.println("Answers: " + ArrayUtils.toString(answers));

    double[][] badCoefficients = { { 1, 1, 1 }, { 1, 1, 1 }, { 1, 1, 1 } };

    double[] badValues = { 0, 1, 3 };

    matrix = new RealMatrixImpl(badCoefficients);

    answers = matrix.solve(badValues);/*from w w  w.j av a  2  s. c  o m*/

    System.out.println("Answers: " + ArrayUtils.toString(answers));

}

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From source file:com.facebook.infrastructure.service.StorageService.java

/**
 * Get the estimated disk space of the target endpoint in its primary range.
 * /*from  ww  w.  ja v  a 2s .  co m*/
 * @param target
 *          whose primary range we are interested in.
 * @return disk space of the target in the primary range.
 */
private double getDiskSpaceForPrimaryRange(EndPoint target) {
    double primaryDiskSpace = 0d;
    Map<BigInteger, EndPoint> tokenToEndPointMap = tokenMetadata_.cloneTokenEndPointMap();
    Set<BigInteger> tokens = tokenToEndPointMap.keySet();
    Range[] allRanges = getAllRanges(tokens);
    Arrays.sort(allRanges);
    /* Mapping from Range to its ordered position on the ring */
    Map<Range, Integer> rangeIndex = new HashMap<Range, Integer>();
    for (int i = 0; i < allRanges.length; ++i) {
        rangeIndex.put(allRanges[i], i);
    }
    /* Get the coefficients for the equations */
    List<double[]> equations = new ArrayList<double[]>();
    /* Get the endpoint to range map */
    Map<EndPoint, List<Range>> endPointToRangesMap = constructEndPointToRangesMap();
    Set<EndPoint> eps = endPointToRangesMap.keySet();

    for (EndPoint ep : eps) {
        List<Range> ranges = endPointToRangesMap.get(ep);
        double[] equation = new double[allRanges.length];
        for (Range range : ranges) {
            int index = rangeIndex.get(range);
            equation[index] = 1;
        }
        equations.add(equation);
    }
    double[][] coefficients = equations.toArray(new double[0][0]);

    /* Get the constants which are the aggregate disk space for each endpoint */
    double[] constants = new double[allRanges.length];
    int index = 0;
    for (EndPoint ep : eps) {
        /* reset the port back to control port */
        ep.setPort(DatabaseDescriptor.getControlPort());
        String lInfo = null;
        if (ep.equals(StorageService.udpAddr_))
            lInfo = getLoadInfo();
        else
            lInfo = getLoadInfo(ep);
        LoadInfo li = new LoadInfo(lInfo);
        constants[index++] = FileUtils.stringToFileSize(li.diskSpace());
    }

    RealMatrix matrix = new RealMatrixImpl(coefficients);
    double[] solutions = matrix.solve(constants);
    Range primaryRange = getPrimaryRangeForEndPoint(target);
    primaryDiskSpace = solutions[rangeIndex.get(primaryRange)];
    return primaryDiskSpace;
}

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