// Ceres Solver - A fast non-linear least squares minimizer
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// http://code.google.com/p/ceres-solver/
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// Author: vitus@google.com (Michael Vitus)

#include "ceres/internal/householder_vector.h"

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

namespace ceres::internal {

static void HouseholderTestHelper(const Vector& x) {
  const double kTolerance = 1e-14;

  // Check to ensure that H * x = ||x|| * [0 ... 0 1]'.
  Vector v(x.rows());
  double beta;

  // NOTE: The explicit template arguments are needed here because
  // ComputeHouseholderVector is templated and some versions of MSVC
  // have trouble deducing the type of v automatically.
  ComputeHouseholderVector<Vector, double, Eigen::Dynamic>(x, &v, &beta);
  Vector result = x - beta * v * (v.transpose() * x);

  Vector expected_result(x.rows());
  expected_result.setZero();
  expected_result(x.rows() - 1) = 1;
  expected_result *= x.norm();

  for (int i = 0; i < x.rows(); ++i) {
    EXPECT_NEAR(expected_result[i], result[i], kTolerance);
  }
}

TEST(HouseholderVector, ZeroPositive) {
  Vector x(3);
  x << 0.0, 0.0, 0.25;

  HouseholderTestHelper(x);
}

TEST(HouseholderVector, ZeroNegative) {
  Vector x(3);
  x << 0.0, 0.0, -0.25;

  HouseholderTestHelper(x);
}

TEST(HouseholderVector, NearZeroPositive) {
  Vector x(3);
  x << 1e-18, 1e-18, 0.25;

  HouseholderTestHelper(x);
}

TEST(HouseholderVector, NearZeroNegative) {
  Vector x(3);
  x << 1e-18, 1e-18, -0.25;

  HouseholderTestHelper(x);
}

TEST(HouseholderVector, NonZeroNegative) {
  Vector x(3);
  x << 1.0, 0.0, -3.0;

  HouseholderTestHelper(x);
}

TEST(HouseholderVector, NonZeroPositive) {
  Vector x(3);
  x << 1.0, 1.0, 1.0;

  HouseholderTestHelper(x);
}

TEST(HouseholderVector, NonZeroPositive_Size4) {
  Vector x(4);
  x << 1.0, 1.0, 0.0, 2.0;

  HouseholderTestHelper(x);
}

TEST(HouseholderVector, LastElementZero) {
  Vector x(4);
  x << 1.0, 1.0, 0.0, 0.0;

  HouseholderTestHelper(x);
}

}  // namespace ceres::internal