/*
 * (C) Copyright 2013 ECMWF.
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 * In applying this licence, ECMWF does not waive the privileges and immunities
 * granted to it by virtue of its status as an intergovernmental organisation
 * nor does it submit to any jurisdiction.
 */

#include <algorithm>   // generate, is_sorted
#include <functional>  // bind
#include <random>      // mt19937 and uniform_int_distribution
#include <vector>      // vector

#include "atlas/parallel/omp/sort.h"
#include "atlas/util/vector.h"

#include "tests/AtlasTestEnvironment.h"

namespace atlas {
namespace test {


atlas::vector<int> create_random_data(int n) {
    std::random_device r;
    std::seed_seq seed{r(), r(), r(), r(), r(), r(), r(), r()};
    std::mt19937 eng(seed);  // a source of random data

    std::uniform_int_distribution<int> dist;
    atlas::vector<int> v(n);

    std::generate(v.begin(), v.end(), std::bind(dist, eng));
    return v;
}

//-----------------------------------------------------------------------------

CASE("test_sort_little") {
    // Because there is little work to be done, the underlying algorithm will not use OpenMP here.
    auto integers = create_random_data(20);

    SECTION("default order") {
        omp::sort(integers.begin(), integers.end());
        EXPECT(std::is_sorted(integers.begin(), integers.end()));
    }

    SECTION("reverse order") {
        omp::sort(integers.begin(), integers.end(), [](const int& a, const int& b) { return b > a; });
        EXPECT(std::is_sorted(integers.begin(), integers.end(), [](const int& a, const int& b) { return b > a; }));
    }
}

CASE("test_sort_large") {
    // There is enough work to use OpenMP underneith, if ATLAS_HAVE_OMP && OMP_NUM_THREADS > 1
    auto integers = create_random_data(1000000);

    SECTION("default order") {
        omp::sort(integers.begin(), integers.end());
        EXPECT(std::is_sorted(integers.begin(), integers.end()));
    }

    SECTION("reverse order") {
        omp::sort(integers.begin(), integers.end(), [](const int& a, const int& b) { return b > a; });
        EXPECT(std::is_sorted(integers.begin(), integers.end(), [](const int& a, const int& b) { return b > a; }));
    }
}

CASE("test_merge_blocks") {
    // There is enough work to use OpenMP underneith, if ATLAS_HAVE_OMP && OMP_NUM_THREADS > 1

    auto nb_blocks  = 16;
    auto block_size = 100000;
    auto integers   = create_random_data(nb_blocks * block_size);
    std::vector<int> blocks_size(nb_blocks, block_size);

    auto end = integers.begin();
    for (int b = 0; b < nb_blocks; ++b) {
        auto begin = end;
        end        = begin + blocks_size[b];
        omp::sort(begin, end);
    }

    omp::merge_blocks(integers.begin(), integers.end(), blocks_size.begin(), blocks_size.end());
    EXPECT(std::is_sorted(integers.begin(), integers.end()));
}

//-----------------------------------------------------------------------------

}  // namespace test
}  // namespace atlas

int main(int argc, char** argv) {
    return atlas::test::run(argc, argv);
}
