Class ArrayArgs

include/LightGBM/utils/array_args.h:20–193

*/
template<typename VAL_T>
class ArrayArgs {
 public:
  inline static size_t ArgMaxMT(const std::vector<VAL_T>& array) {
    int num_threads = 1;
#pragma omp parallel
#pragma omp master
    {
      num_threads = omp_get_num_threads();
    }
    int step = std::max(1, (static_cast<int>(array.size()) + num_threads - 1) / num_threads);
    std::vector<size_t> arg_maxs(num_threads, 0);
    #pragma omp parallel for schedule(static, 1)
    for (int i = 0; i < num_threads; ++i) {
      size_t start = step * i;
      if (start >= array.size()) { continue; }
      size_t end = std::min(array.size(), start + step);
      size_t arg_max = start;
      for (size_t j = start + 1; j < end; ++j) {
        if (array[j] > array[arg_max]) {
          arg_max = j;
        }
      }
      arg_maxs[i] = arg_max;
    }
    size_t ret = arg_maxs[0];
    for (int i = 1; i < num_threads; ++i) {
      if (array[arg_maxs[i]] > array[ret]) {
        ret = arg_maxs[i];
      }
    }
    return ret;
  }
  inline static size_t ArgMax(const std::vector<VAL_T>& array) {
    if (array.empty()) {
      return 0;
    }
    if (array.size() > 1024) {
      return ArgMaxMT(array);
    } else {
      size_t arg_max = 0;
      for (size_t i = 1; i < array.size(); ++i) {
        if (array[i] > array[arg_max]) {
          arg_max = i;
        }
      }
      return arg_max;
    }
  }

  inline static size_t ArgMin(const std::vector<VAL_T>& array) {
    if (array.empty()) {
      return 0;
    }
    size_t arg_min = 0;
    for (size_t i = 1; i < array.size(); ++i) {
      if (array[i] < array[arg_min]) {
        arg_min = i;
      }