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package edu.emory.mathcs.jplasma.example;

import edu.emory.mathcs.jplasma.tdouble.Dplasma;
import edu.emory.mathcs.utils.ConcurrencyUtils;

/**
 * Example for solving a system of linear equations using QR factorization.
 * 
 * @author Piotr Wendykier (piotr.wendykier@gmail.com)
 * 
 */
public class DgelsExample {
    public static void main(String[] args) {
        int M = 15;
        int N = 10;
        int NRHS = 5;
        int INFO;
        int i, j;

        double[] A = new double[M * N];
        double[] B = new double[M * NRHS];

        /* Initialize A */
        for (i = 0; i < M; i++)
            for (j = 0; j < N; j++)
                A[M * j + i] = 0.5 - Math.random();

        /* Initialize B */
        for (i = 0; i < M; i++)
            for (j = 0; j < NRHS; j++)
                B[M * j + i] = Math.random();

        /* (Optional step) Set the maximum number of threads. It has to be called before plasma_Init().
         * By default, the maximum number of threads is equal to the number of available processors. */
        ConcurrencyUtils.setNumberOfThreads(4);

        /* Plasma Initialize */
        Dplasma.plasma_Init(M, N, NRHS);

        /* (Optional step) Set the number of threads used in computations. It has to be called after plasma_Init().
         * By default, the number of threads used in computations is equal to the number of available processors. */
        Dplasma.plasma_set_int(Dplasma.PLASMA_CONCURRENCY, 2);

        /* Allocate T */
        double[] T = Dplasma.plasma_Allocate_T(M, N);

        /* Solve the problem */
        INFO = Dplasma.plasma_DGELS(Dplasma.PlasmaNoTrans, M, N, NRHS, A, 0, M, T, 0, B, 0, M);

        /* Plasma Finalize */
        Dplasma.plasma_Finalize();

        if (INFO < 0)
            System.err.println("-- Error in DgelsExample example !");
        else
            System.out.println("-- Run successfull !");

        System.exit(0);
    }
}