import edu.rice.hj.api.HjMetrics;
import edu.rice.hj.runtime.config.HjSystemProperty;
import edu.rice.hj.runtime.metrics.AbstractMetricsManager;

import java.util.Random;

import static edu.rice.hj.Module1.*;

/**
 * ArraySum1.hj --- Parallel iterative example program for computing the sum of an array
 *
 * This example program creates an array of n random int's, and computes their sum in parallel.
 * The default value of n is 8, but any array size can be provided as argv[0]
 * by going into the run configuration and putting it in the program arguments field on
 * intelliJ, or by typing java ArraySum1 n on the command line
 *
 * To obtain abstract performance metrics, select the appropriate compiler option.
 *
 * NOTE: this example program is for illustrative purposes, and is not intended to be used as a performance benchmark.
 *
 * @author Vivek Sarkar (vsarkar@rice.edu)
 */
public class ArraySum1 {
    static final int default_n = 8;
    static final String err = "Incorrect argument for array size (should be > 0), assuming n = " + default_n;

    /**
     * Main method, runs the ArraySum
     * @param argv - the input parameters
     */
    public static void main(String[] argv) {

        // Setup metrics
        
        initializeHabanero();

        // Initialization
        int n;
        int[] X;
        if (argv.length != 0) {
            try {
                n = Integer.parseInt(argv[0]);
                if (n <= 0) {
                    // Bad value of n
                    System.out.println(err);
                    n = default_n;
                }
            } catch (Throwable e) {
                System.out.println(err);
                n = default_n;
            }
        } else { // argv.length == 0
            n = default_n;
        }
        X = new int[n];
        Random myRand = new Random(n);

        for (int i = 0; i < n; i++) {
            X[i] = myRand.nextInt(n);
        }

        // Parallel reduction
        for (int step = 1; step < n; step *= 2) {
            int size = ceilDiv(n, 2 * step);
            final int sstep = step;
            finish(() -> {
                for (int i = 0; i < size; i++) {
                    final int ii = i;
                    async(() -> {
                        // if condition ensures that algorithm works correctly when X.length is not a power of 2
                        if ((2 * ii + 1) * sstep < X.length) {
                            doWork(1); // count each + operator as 1 unit of work in the abstract performance metrics
                            // local variables X, step, size are copied on entry to the async, analogous to method call parameters
                            X[2 * ii * sstep] += X[(2 * ii + 1) * sstep];
                        }
                    });
                }
            }); // finish-for-async
        }

        // Output
        System.out.println("Sum of " + n + " elements = " + X[0] + " (should be 27 for n = 8)");

        // Print out the metrics data
        finalizeHabanero();
        final HjMetrics actualMetrics = abstractMetrics();
        AbstractMetricsManager.dumpStatistics(actualMetrics);
        System.out.println(actualMetrics);

    }
    
    /**
     * Divide x by y, and round up to next largest int
     * @param x - dividend
     * @param y - divisor
     * @return quotient rounded to the up to an integer
     */
    static int ceilDiv(int x, int y) {
        return (x + y - 1) / y;
    }

}