ceres-solver/internal/ceres/parallel_for_test.cc

// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2018 Google Inc. All rights reserved.
// http://ceres-solver.org/
//
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// modification, are permitted provided that the following conditions are met:
//
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//   this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
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// Author: vitus@google.com (Michael Vitus)

// This include must come before any #ifndef check on Ceres compile options.
#include "ceres/internal/port.h"

#if defined(CERES_USE_TBB) || defined(CERES_USE_CXX11_THREADS)

#include "ceres/parallel_for.h"

#include <vector>

#include "ceres/context_impl.h"
#include "gmock/gmock.h"
#include "gtest/gtest.h"

namespace ceres {
namespace internal {

using testing::ElementsAreArray;

// Tests the parallel for loop computes the correct result for various number of
// threads.
TEST(ParallelFor, NumThreads) {
  ContextImpl context;
  context.EnsureMinimumThreads(/*num_threads=*/2);

  const int size = 16;
  std::vector<int> expected_results(size, 0);
  for (int i = 0; i < size; ++i) {
    expected_results[i] = std::sqrt(i);
  }

  for (int num_threads = 1; num_threads <= 8; ++num_threads) {
    std::vector<int> values(size, 0);
    ParallelFor(&context, 0, size, num_threads,
                [&values](int i) { values[i] = std::sqrt(i); });
    EXPECT_THAT(values, ElementsAreArray(expected_results));
  }
}

// Tests nested for loops do not result in a deadlock.
TEST(ParallelFor, NestedParallelForDeadlock) {
  ContextImpl context;
  context.EnsureMinimumThreads(/*num_threads=*/2);

  // Increment each element in the 2D matrix.
  std::vector<std::vector<int>> x(3, {1, 2, 3});
  ParallelFor(&context, 0, 3, 2, [&x, &context](int i) {
    std::vector<int>& y = x.at(i);
    ParallelFor(&context, 0, 3, 2, [&y](int j) { ++y.at(j); });
  });

  const std::vector<int> results = {2, 3, 4};
  for (const std::vector<int>& value : x) {
    EXPECT_THAT(value, ElementsAreArray(results));
  }
}

}  // namespace internal
}  // namespace ceres

#endif // defined(CERES_USE_TBB) || defined(CERES_USE_CXX11_THREADS)