xref: /oneTBB/examples/graph/som/som_graph.cpp (revision e1b24895)

/*
    Copyright (c) 2005-2021 Intel Corporation

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
*/

//
// Self-organizing map in TBB flow::graph
//
//   This is an example of the use of cancellation in a graph.  After a point in searching for
//   the best match for an example, two examples are looked for simultaneously.  When the
//   earlier example is found and the update radius is determined, the affected searches
//   for the subsequent example are cancelled, and after the update they are restarted.
//   As the update radius shrinks fewer searches are cancelled, and by the last iterations
//   virtually all the work done for the speculating example is useful.
//
// first, a simple implementation with only one example vector
// at a time.
//
// we will do a color map (the simple example.)
//
//  graph algorithm
//
//       for some number of iterations
//           update radius r, weight of change L
//           for each example V
//               use graph to find BMU
//               for each part of map within radius of BMU W
//                   update vector:  W(t+1) = W(t) + w(dist)*L*(V - W(t))

#ifndef NOMINMAX
#define NOMINMAX
#endif // NOMINMAX

#include <algorithm>

#define _MAIN_C_ 1
#include "som.hpp"

#include "oneapi/tbb/flow_graph.h"
#include "oneapi/tbb/blocked_range2d.h"
#include "oneapi/tbb/tick_count.h"
#include "oneapi/tbb/task_arena.h"
#include "oneapi/tbb/global_control.h"

#include "common/utility/utility.hpp"
#include "common/utility/get_default_num_threads.hpp"

#define RED   0
#define GREEN 1
#define BLUE  2

static int xranges = 1;
static int yranges = 1;
static int xsize = -1;
static int ysize = -1;

static int global_i = 0;
static int speculation_start;

#if EXTRA_DEBUG
std::vector<int> cancel_count;
std::vector<int> extra_count;
std::vector<int> missing_count;
std::vector<int> canceled_before;
#endif
std::vector<int> function_node_execs;
static int xRangeMax = 3;
static int yRangeMax = 3;
static bool dont_speculate = false;
static search_result_type last_update;

class BMU_search_body {
    SOMap &my_map;
    subsquare_type my_square;
    int &fn_tally;

public:
    BMU_search_body(SOMap &_m, subsquare_type &_sq, int &fnt)
            : my_map(_m),
              my_square(_sq),
              fn_tally(fnt) {}
    BMU_search_body(const BMU_search_body &other)
            : my_map(other.my_map),
              my_square(other.my_square),
              fn_tally(other.fn_tally) {}
    search_result_type operator()(const SOM_element s) {
        int my_x;
        int my_y;
        double min_dist = my_map.BMU_range(s, my_x, my_y, my_square);
        ++fn_tally; // count how many times this function_node executed
        return search_result_type(min_dist, my_x, my_y);
    }
};

typedef oneapi::tbb::flow::function_node<SOM_element, search_result_type> search_node;
typedef oneapi::tbb::flow::broadcast_node<SOM_element> b_node;
typedef std::vector<search_node *> search_node_vector_type;
typedef std::vector<search_node_vector_type> search_node_array_type;
typedef std::vector<oneapi::tbb::flow::graph *> graph_vector_type;
typedef std::vector<graph_vector_type> graph_array_type;

#define SPECULATION_CNT 2

oneapi::tbb::flow::graph *g[SPECULATION_CNT]; // main graph; there should only be one per epoch
b_node *send_to[SPECULATION_CNT]; // broadcast node to send exemplar to all function_nodes
oneapi::tbb::flow::queue_node<search_result_type>
    *q[SPECULATION_CNT]; // queue for function nodes to put their results in
// each function_node should have its own graph
search_node_array_type *s_array[SPECULATION_CNT]; // 2d array of function nodes
graph_array_type *g_array[SPECULATION_CNT]; // 2d array of graphs

// All graphs must locate in the same arena.
oneapi::tbb::flow::graph *construct_graph(oneapi::tbb::task_arena &ta) {
    oneapi::tbb::flow::graph *result;
    ta.execute([&result] {
        result = new oneapi::tbb::flow::graph();
    });
    return result;
}

// build a set of SPECULATION_CNT graphs, each of which consists of a broadcast_node,
//    xranges x yranges function_nodes, and one queue_node for output.
//    once speculation starts, if i % SPECULATION_CNT is the current graph, (i+1) % SPECULATION_CNT
//    is the first speculation, and so on.
void build_BMU_graph(SOMap &map1, oneapi::tbb::task_arena &ta) {
    // build current graph
    xsize = ((int)map1.size() + xranges - 1) / xranges;
    ysize = ((int)map1[0].size() + yranges - 1) / yranges;
    function_node_execs.clear();
    function_node_execs.reserve(xranges * yranges + 1);
    for (int i = 0; i < xranges * yranges + 1; ++i)
        function_node_execs.push_back(0);

    for (int scnt = 0; scnt < SPECULATION_CNT; ++scnt) {
        g[scnt] = construct_graph(ta);
        send_to[scnt] = new b_node(*(g[scnt])); // broadcast node to the function_nodes
        q[scnt] = new oneapi::tbb::flow::queue_node<search_result_type>(*(g[scnt])); // output queue

        // create the function_nodes, tie to the graph
        s_array[scnt] = new search_node_array_type;
        s_array[scnt]->reserve(xranges);
        g_array[scnt] = new graph_array_type;
        g_array[scnt]->reserve(xranges);
        for (int i = 0; i < (int)map1.size(); i += xsize) {
            int xindex = i / xsize;
            s_array[scnt]->push_back(search_node_vector_type());
#if EXTRA_DEBUG
            if (s_array[scnt]->size() != xindex + 1) {
                printf("Error; s_array[%d]->size() == %d, xindex== %d\n",
                       scnt,
                       (int)(s_array[scnt]->size()),
                       xindex);
            }
#endif
            (*s_array[scnt])[xindex].reserve(yranges);
            g_array[scnt]->push_back(graph_vector_type());
            (*g_array[scnt])[xindex].reserve(yranges);
            for (int j = 0; j < (int)map1[0].size(); j += ysize) {
                int offset = (i / xsize) * yranges + (j / ysize);
                int xmax = (i + xsize) > (int)map1.size() ? (int)map1.size() : i + xsize;
                int ymax = (j + ysize) > (int)map1[0].size() ? (int)map1[0].size() : j + ysize;
                subsquare_type sst(i, xmax, 1, j, ymax, 1);
                BMU_search_body bb(map1, sst, function_node_execs[offset]);
                oneapi::tbb::flow::graph *g_local = construct_graph(ta);
                search_node *s =
                    new search_node(*g_local, oneapi::tbb::flow::serial, bb); // copies Body
                (*g_array[scnt])[xindex].push_back(g_local);
                (*s_array[scnt])[xindex].push_back(s);
                oneapi::tbb::flow::make_edge(*(send_to[scnt]),
                                             *s); // broadcast_node -> function_node
                oneapi::tbb::flow::make_edge(*s, *(q[scnt])); // function_node -> queue_node
            }
        }
    }
}

// Wait for the 2D array of flow::graphs.
void wait_for_all_graphs(int cIndex) { // cIndex ranges over [0 .. SPECULATION_CNT - 1]
    for (int x = 0; x < xranges; ++x) {
        for (int y = 0; y < yranges; ++y) {
            (*g_array[cIndex])[x][y]->wait_for_all();
        }
    }
}

void destroy_BMU_graph() {
    for (int scnt = 0; scnt < SPECULATION_CNT; ++scnt) {
        for (int i = 0; i < (int)(*s_array[scnt]).size(); ++i) {
            for (int j = 0; j < (int)(*s_array[scnt])[i].size(); ++j) {
                delete (*s_array[scnt])[i][j];
                delete (*g_array[scnt])[i][j];
            }
        }
        (*s_array[scnt]).clear();
        delete s_array[scnt];
        (*g_array[scnt]).clear();
        delete g_array[scnt];
        delete q[scnt];
        delete send_to[scnt];
        delete g[scnt];
    }
}

void find_subrange_overlap(int const &xval,
                           int const &yval,
                           double const &radius,
                           int &xlow,
                           int &xhigh,
                           int &ylow,
                           int &yhigh) {
    xlow = int((xval - radius) / xsize);
    xhigh = int((xval + radius) / xsize);
    ylow = int((yval - radius) / ysize);
    yhigh = int((yval + radius) / ysize);
    // circle may fall partly outside map
    if (xlow < 0)
        xlow = 0;
    if (xhigh >= xranges)
        xhigh = xranges - 1;
    if (ylow < 0)
        ylow = 0;
    if (yhigh >= yranges)
        yhigh = yranges - 1;
#if EXTRA_DEBUG
    if (xlow >= xranges)
        printf(" Error *** xlow == %d\n", xlow);
    if (xhigh < 0)
        printf("Error *** xhigh == %d\n", xhigh);
    if (ylow >= yranges)
        printf("Error *** ylow == %d\n", ylow);
    if (yhigh < 0)
        printf("Error *** yhigh == %d\n", yhigh);
#endif
}

bool overlap(int &xval, int &yval, search_result_type &sr) {
    int xlow, xhigh, ylow, yhigh;
    find_subrange_overlap(
        std::get<XV>(sr), std::get<YV>(sr), std::get<RADIUS>(sr), xlow, xhigh, ylow, yhigh);
    return xval >= xlow && xval <= xhigh && yval >= ylow && yval <= yhigh;
}

void cancel_submaps(int &xval, int &yval, double &radius, int indx) {
    int xlow;
    int xhigh;
    int ylow;
    int yhigh;
    find_subrange_overlap(xval, yval, radius, xlow, xhigh, ylow, yhigh);
    for (int x = xlow; x <= xhigh; ++x) {
        for (int y = ylow; y <= yhigh; ++y) {
            (*g_array[indx])[x][y]->cancel();
        }
    }
#if EXTRA_DEBUG
    ++cancel_count[(xhigh - xlow + 1) * (yhigh - ylow + 1)];
#endif
}

void restart_submaps(int &xval, int &yval, double &radius, int indx, SOM_element &vector) {
    int xlow;
    int xhigh;
    int ylow;
    int yhigh;
    find_subrange_overlap(xval, yval, radius, xlow, xhigh, ylow, yhigh);
    for (int x = xlow; x <= xhigh; ++x) {
        for (int y = ylow; y <= yhigh; ++y) {
            // have to reset the graph
            (*g_array[indx])[x][y]->reset();
            // and re-submit the exemplar for search.
            (*s_array[indx])[x][y]->try_put(vector);
        }
    }
}

search_result_type graph_BMU(int indx) { // indx ranges over [0 .. SPECULATION_CNT -1]
    wait_for_all_graphs(indx); // wait for the array of subgraphs
    (g[indx])->wait_for_all();
    std::vector<search_result_type> all_srs(xRangeMax * yRangeMax,
                                            search_result_type(DBL_MAX, -1, -1));
#if EXTRA_DEBUG
    int extra_computations = 0;
#endif
    search_result_type sr;
    search_result_type min_sr;
    std::get<RADIUS>(min_sr) = DBL_MAX;
    int result_count = 0;
    while ((q[indx])->try_get(sr)) {
        ++result_count;
        // figure which submap this came from
        int x = std::get<XV>(sr) / xsize;
        int y = std::get<YV>(sr) / ysize;
#if EXTRA_DEBUG
        if (x < 0 || x >= xranges)
            printf(" ###  x value out of range (%d)\n", x);
        if (y < 0 || y >= yranges)
            printf(" ###  y value out of range (%d)\n", y);
#endif
        int offset = x * yranges + y; // linearized subscript
#if EXTRA_DEBUG
        if (std::get<RADIUS>(all_srs[offset]) !=
            DBL_MAX) { // we've already got a result from this subsquare
            ++extra_computations;
        }
        else if (std::get<XV>(all_srs[offset]) != -1) {
            if (extra_debug)
                printf("More than one cancellation of [%d,%d] iteration %d\n", x, y, global_i);
        }
#endif
        all_srs[offset] = sr;
        if (std::get<RADIUS>(sr) < std::get<RADIUS>(min_sr))
            min_sr = sr;
        else if (std::get<RADIUS>(sr) == std::get<RADIUS>(min_sr)) {
            if (std::get<XV>(sr) < std::get<XV>(min_sr)) {
                min_sr = sr;
            }
            else if ((std::get<XV>(sr) == std::get<XV>(min_sr) &&
                      std::get<YV>(sr) < std::get<YV>(min_sr))) {
                min_sr = sr;
            }
        }
    }
#if EXTRA_DEBUG
    if (result_count != xranges * yranges + extra_computations) {
        // we are missing at least one of the expected results.  Tally the missing values
        for (int i = 0; i < xranges * yranges; ++i) {
            if (std::get<RADIUS>(all_srs[i]) == DBL_MAX) {
                // i == x*yranges + y
                int xval = i / yranges;
                int yval = i % yranges;
                bool received_cancel_result = std::get<XV>(all_srs[i]) != -1;
                if (overlap(xval, yval, last_update)) {
                    // we have previously canceled this subsquare.
                    printf("No result for [%d,%d] which was canceled(%s)\n",
                           xval,
                           yval,
                           received_cancel_result ? "T" : "F");
                    ++canceled_before[i];
                }
                else {
                    printf("No result for [%d,%d] which was not canceled(%s)\n",
                           xval,
                           yval,
                           received_cancel_result ? "T" : "F");
                }
                ++missing_count[i];
            }
        }
    }
    if (extra_computations)
        ++extra_count[extra_computations];
#endif
    return min_sr;
    // end of one epoch
}

void graph_teach(SOMap &map1, teaching_vector_type &in, oneapi::tbb::task_arena &ta) {
    build_BMU_graph(map1, ta);
#if EXTRA_DEBUG
    cancel_count.clear();
    extra_count.clear();
    missing_count.clear();
    canceled_before.clear();
    cancel_count.reserve(xRangeMax * yRangeMax + 1);
    extra_count.reserve(xRangeMax * yRangeMax + 1);
    missing_count.reserve(xRangeMax * yRangeMax + 1);
    canceled_before.reserve(xRangeMax * yRangeMax + 1);
    for (int i = 0; i < xRangeMax * yRangeMax + 1; ++i) {
        cancel_count.push_back(0);
        extra_count.push_back(0);
        missing_count.push_back(0);
        canceled_before.push_back(0);
    }
#endif
    // normally the training would pick random exemplars to teach the SOM.  We need
    // the process to be reproducible, so we will pick the exemplars in order, [0, in.size())
    int next_j = 0;
    for (int epoch = 0; epoch < nPasses; ++epoch) {
        global_i = epoch;
        bool canceled_submaps = false;
        int j = next_j; // try to make reproducible
        next_j = (epoch + 1) % in.size();
        search_result_type min_sr;
        if (epoch < speculation_start) {
            (send_to[epoch % SPECULATION_CNT])->try_put(in[j]);
        }
        else if (epoch == speculation_start) {
            (send_to[epoch % SPECULATION_CNT])->try_put(in[j]);
            if (epoch < nPasses - 1) {
                (send_to[(epoch + 1) % SPECULATION_CNT])->try_put(in[next_j]);
            }
        }
        else if (epoch < nPasses - 1) {
            (send_to[(epoch + 1) % SPECULATION_CNT])->try_put(in[next_j]);
        }
        min_sr = graph_BMU(epoch % SPECULATION_CNT); //calls wait_for_all()
        double min_distance = std::get<0>(min_sr);
        double radius = max_radius * exp(-(double)epoch * radius_decay_rate);
        double learning_rate = max_learning_rate * exp(-(double)epoch * learning_decay_rate);
        if (epoch >= speculation_start && epoch < (nPasses - 1)) {
            // have to cancel the affected submaps
            cancel_submaps(
                std::get<XV>(min_sr), std::get<YV>(min_sr), radius, (epoch + 1) % SPECULATION_CNT);
            canceled_submaps = true;
        }
        map1.epoch_update(
            in[j], epoch, std::get<1>(min_sr), std::get<2>(min_sr), radius, learning_rate);
        ++global_i;
        if (canceled_submaps) {
            // do I have to wait for all the non-canceled speculative graph to complete first?
            // yes, in case a canceled task was already executing.
            wait_for_all_graphs((epoch + 1) % SPECULATION_CNT); // wait for the array of subgraphs
            restart_submaps(std::get<1>(min_sr),
                            std::get<2>(min_sr),
                            radius,
                            (epoch + 1) % SPECULATION_CNT,
                            in[next_j]);
        }

        last_update = min_sr;
        std::get<RADIUS>(last_update) = radius; // not smallest value, but range of effect
    }
    destroy_BMU_graph();
}

static const double serial_time_adjust = 1.25;
static double radius_fraction = 3.0;

int main(int argc, char *argv[]) {
    int l_speculation_start;
    utility::thread_number_range threads(
        utility::get_default_num_threads,
        utility::
            get_default_num_threads() // run only the default number of threads if none specified
    );

    utility::parse_cli_arguments(
        argc,
        argv,
        utility::cli_argument_pack()
            //"-h" option for for displaying help is present implicitly
            .positional_arg(
                threads,
                "n-of-threads",
                "number of threads to use; a range of the form low[:high], where low and optional high are non-negative integers or 'auto' for the TBB default.")
            // .positional_arg(InputFileName,"input-file","input file name")
            // .positional_arg(OutputFileName,"output-file","output file name")
            .positional_arg(
                radius_fraction, "radius-fraction", "size of radius at which to start speculating")
            .positional_arg(
                nPasses, "number-of-epochs", "number of examples used in learning phase")
            .arg(cancel_test, "cancel-test", "test for cancel signal while finding BMU")
            .arg(extra_debug, "debug", "additional output")
            .arg(dont_speculate, "nospeculate", "don't speculate in SOM map teaching"));

    readInputData();
    max_radius = (xMax < yMax) ? yMax / 2 : xMax / 2;
    // need this value for the 1x1 timing below
    radius_decay_rate = -(log(1.0 / (double)max_radius) / (double)nPasses);
    find_data_ranges(my_teaching, max_range, min_range);
    if (extra_debug) {
        printf("Data range: ");
        remark_SOM_element(min_range);
        printf(" to ");
        remark_SOM_element(max_range);
        printf("\n");
    }

    // find how much time is taken for the single function_node case.
    // adjust nPasses so the 1x1 time is somewhere around serial_time_adjust seconds.
    // make sure the example test runs for at least 0.5 second.
    for (;;) {
        // Restrict max concurrency level via task_arena interface
        oneapi::tbb::task_arena ta(1);
        SOMap map1(xMax, yMax);
        speculation_start = nPasses + 1; // Don't speculate

        xranges = 1;
        yranges = 1;
        map1.initialize(InitializeGradient, max_range, min_range);
        oneapi::tbb::tick_count t0 = oneapi::tbb::tick_count::now();
        graph_teach(map1, my_teaching, ta);
        oneapi::tbb::tick_count t1 = oneapi::tbb::tick_count::now();
        double nSeconds = (t1 - t0).seconds();
        if (nSeconds < 0.5) {
            xMax *= 2;
            yMax *= 2;
            continue;
        }
        double size_adjust = sqrt(serial_time_adjust / nSeconds);
        xMax = (int)((double)xMax * size_adjust);
        yMax = (int)((double)yMax * size_adjust);
        max_radius = (xMax < yMax) ? yMax / 2 : xMax / 2;
        radius_decay_rate = log((double)max_radius) / (double)nPasses;

        if (extra_debug) {
            printf("original 1x1 case ran in %g seconds\n", nSeconds);
            printf("   Size of table == %d x %d\n", xMax, yMax);
            printf("   radius_decay_rate == %g\n", radius_decay_rate);
        }
        break;
    }

    // the "max_radius" starts at 1/2*radius_fraction the table size.  To start the speculation when the radius is
    // 1 / n * the table size, the constant in the log below should be n / 2.  so 2 == 1/4, 3 == 1/6th,
    // et c.
    if (dont_speculate) {
        l_speculation_start = nPasses + 1;
        if (extra_debug)
            printf("speculation will not be done\n");
    }
    else {
        if (radius_fraction < 1.0) {
            if (extra_debug)
                printf("Warning: radius_fraction should be >= 1.  Setting to 1.\n");
            radius_fraction = 1.0;
        }
        l_speculation_start = (int)((double)nPasses * log(radius_fraction) / log((double)nPasses));
        if (extra_debug)
            printf("We will start speculation at iteration %d\n", l_speculation_start);
    }
    double single_time; // for speedup calculations
#if EXTRA_DEBUG
    // storage for the single-subrange answers, for comparing maps
    std::vector<double> single_dist;
    single_dist.reserve(my_teaching.size());
    std::vector<int> single_xval;
    single_xval.reserve(my_teaching.size());
    std::vector<int> single_yval;
    single_yval.reserve(my_teaching.size());
#endif
    //TODO: Investigate how to not require mandatory concurrency
    for (int p = std::max(threads.first, 2); p <= std::max(threads.last, 2); ++p) {
        // Restrict max concurrency level via task_arena interface
        oneapi::tbb::global_control limit(oneapi::tbb::global_control::max_allowed_parallelism, p);
        oneapi::tbb::task_arena ta(p);
        if (extra_debug)
            printf(" -------------- Running with %d threads. ------------\n", p);
        // run the SOM build for a series of subranges
        for (xranges = 1; xranges <= xRangeMax; ++xranges) {
            for (yranges = xranges; yranges <= yRangeMax; ++yranges) {
                if (xranges == 1 && yranges == 1) {
                    // don't pointlessly speculate if we're only running one subrange.
                    speculation_start = nPasses + 1;
                }
                else {
                    speculation_start = l_speculation_start;
                }
                SOMap map1(xMax, yMax);
                map1.initialize(InitializeGradient, max_range, min_range);

                if (extra_debug)
                    printf("Start learning for [%d,%d] ----------- \n", xranges, yranges);
                oneapi::tbb::tick_count t0 = oneapi::tbb::tick_count::now();
                graph_teach(map1, my_teaching, ta);
                oneapi::tbb::tick_count t1 = oneapi::tbb::tick_count::now();

                if (extra_debug)
                    printf("Done learning for [%d,%d], which took %g seconds ",
                           xranges,
                           yranges,
                           (t1 - t0).seconds());
                if (xranges == 1 && yranges == 1)
                    single_time = (t1 - t0).seconds();
                if (extra_debug)
                    printf(": speedup == %g\n", single_time / (t1 - t0).seconds());

#if EXTRA_DEBUG
                if (extra_debug) {
                    // number of times cancel was called, indexed by number of subranges canceled
                    for (int i = 0; i < cancel_count.size(); ++i) {
                        // only write output if we have a non-zero value.
                        if (cancel_count[i] > 0) {
                            int totalcnt = 0;
                            printf("     cancellations: ");
                            for (int j = 0; j < cancel_count.size(); ++j) {
                                if (cancel_count[j]) {
                                    printf(" %d [%d]", j, cancel_count[j]);
                                    totalcnt += cancel_count[j];
                                }
                            }
                            totalcnt += speculation_start;
                            printf(" for a total of %d\n", totalcnt);
                            break; // from for
                        }
                    }

                    // number of extra results (these occur when the subrange task starts before
                    // cancel is received.)
                    for (int i = 0; i < extra_count.size(); ++i) {
                        if (extra_count[i] > 0) {
                            int totalcnt = 0;
                            printf("extra computations: ");
                            for (int j = 0; j < extra_count.size(); ++j) {
                                if (extra_count[j]) {
                                    printf(" %d[%d]", j, extra_count[j]);
                                    totalcnt += extra_count[j];
                                }
                            }
                            totalcnt += speculation_start;
                            printf(" for a total of %d\n", totalcnt);
                            break; // from for
                        }
                    }

                    // here we count the number of times we looked for a particular subrange when fetching
                    // the queue_node output and didn't find anything.  This may occur when a function_node
                    // is "stuck" and doesn't process some number of exemplars.  function_node_execs is
                    // a count of the number of times the corresponding function_node was executed (in
                    // case the problem is dropped output in the queue_node.)
                    for (int i = 0; i < missing_count.size(); ++i) {
                        if (missing_count[i]) {
                            int xval = i / yranges;
                            int yval = i % yranges;
                            printf(" f_node[%d,%d] missed %d values", xval, yval, missing_count[i]);
                            if (canceled_before[i]) {
                                printf(" canceled_before == %d", canceled_before[i]);
                            }
                            printf(", fn_tally == %d\n", function_node_execs[i]);
                        }
                    }
                }

                // check that output matches the 1x1 case
                for (int i = 0; i < my_teaching.size(); ++i) {
                    int xdist;
                    int ydist;
                    double my_dist = map1.BMU(my_teaching[i], xdist, ydist);
                    if (xranges == 1 && yranges == 1) {
                        single_dist.push_back(my_dist);
                        single_xval.push_back(xdist);
                        single_yval.push_back(ydist);
                    }
                    else {
                        if (single_dist[i] != my_dist || single_xval[i] != xdist ||
                            single_yval[i] != ydist)
                            printf(
                                "Error in output: expecting <%g, %d, %d>, but got <%g, %d, %d>\n",
                                single_dist[i],
                                single_xval[i],
                                single_yval[i],
                                my_dist,
                                xdist,
                                ydist);
                    }
                }
#endif
            } // yranges
        } // xranges
    } // #threads p
    printf("done\n");
    return 0;
}