/*
----
This file is NOT part of SECONDO.
Authors: Greg Hamerly and Jonathan Drake
Feedback: hamerly@cs.baylor.edu
See: http://cs.baylor.edu/~hamerly/software/kmeans.php
Copyright 2014
----

//paragraph [1] Title: [{\Large \bf \begin{center}] [\end{center}}]
//[TOC] [\tableofcontents]

[1] Implementation of the naive kmeans algorithm


1 Implementation of the naive kmeans algorithm

*/

/* Authors: Greg Hamerly and Jonathan Drake
 * Feedback: hamerly@cs.baylor.edu
 * See: http://cs.baylor.edu/~hamerly/software/kmeans.php
 * Copyright 2014
 */

#include "naive_kmeans.h"
#include "general_functions.h"
#include <cassert>
#include <cstring>

/* The classic algorithm of assign, move, repeat. No optimizations that prune
 * the search.
 *
 * Return value: the number of iterations performed (always at least 1)
 */

int NaiveKmeans::runThread(int threadId, int maxIterations) {
    // track the number of iterations the algorithm performs
    int iterations = 0;

    int startNdx = start(threadId);
    int endNdx = end(threadId);

    while ((iterations < maxIterations) && (! converged)) {
        ++iterations;

        // loop over all examples
        for (int i = startNdx; i < endNdx; ++i) {
            // look for the closest center to this example
            int closest = 0;
            double closestDist2 = std::numeric_limits<double>::max();
            for (int j = 0; j < k; ++j) {
                double d2 = pointCenterDist2(i, j);
                if (d2 < closestDist2) {
                    closest = j;
                    closestDist2 = d2;
                }
            }
            if (assignment[i] != closest) {
                changeAssignment(i, closest, threadId);
            }
        }

        verifyAssignment(iterations, startNdx, endNdx);

        synchronizeAllThreads();

        if (threadId == 0) {
            int furthestMovingCenter = move_centers();
            converged = (0.0 == centerMovement[furthestMovingCenter]);
        }

        synchronizeAllThreads();
    }

    return iterations;
}