// Ceres Solver - A fast non-linear least squares minimizer
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// http://ceres-solver.org/
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// Author: wjr@google.com (William Rucklidge)

#include "ceres/parallel_utils.h"

#include "ceres/internal/config.h"
#include "gtest/gtest.h"

namespace ceres::internal {

// Tests that unfolding linear iterations to triangular iterations produces
// indices that are in-range and unique.
TEST(LinearIndexToUpperTriangularIndexTest, UniqueAndValid) {
  for (int n = 0; n < 100; n++) {
    std::set<std::pair<int, int>> seen_pairs;
    int actual_work_items = (n * (n + 1)) / 2;
    for (int k = 0; k < actual_work_items; k++) {
      int i, j;
      LinearIndexToUpperTriangularIndex(k, n, &i, &j);
      EXPECT_GE(i, 0);
      EXPECT_LT(i, n);
      EXPECT_GE(j, i);
      EXPECT_LT(j, n);
      seen_pairs.insert(std::make_pair(i, j));
    }
    EXPECT_EQ(actual_work_items, seen_pairs.size());
  }
}

}  // namespace ceres::internal