SquareMatrix2.h

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/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
 
#ifndef META_OCEAN_MATH_SQUARE_MATRIX_2_H
#define META_OCEAN_MATH_SQUARE_MATRIX_2_H
 
#include "ocean/math/Math.h"
#include "ocean/math/Equation.h"
#include "ocean/math/Numeric.h"
#include "ocean/math/Vector2.h"
 
#include <vector>
 
namespace Ocean
{
 
// Forward declaration.
template <typename T> class SquareMatrixT2;
 
/**
 * Definition of the SquareMatrix2 object, depending on the OCEAN_MATH_USE_SINGLE_PRECISION either with single or double precision float data type.
 * @see SquareMatrixT2
 * @ingroup math
 */
using SquareMatrix2 = SquareMatrixT2<Scalar>;
 
/**
 * Instantiation of the SquareMatrixT2 template class using a double precision float data type.
 * @see SquareMatrixT2
 * @ingroup math
 */
using SquareMatrixD2 = SquareMatrixT2<double>;
 
/**
 * Instantiation of the SquareMatrixT2 template class using a single precision float data type.
 * @see SquareMatrixT2
 * @ingroup math
 */
using SquareMatrixF2 = SquareMatrixT2<float>;
 
/**
 * Definition of a typename alias for vectors with SquareMatrixT2 objects.
 * @see SquareMatrixT2
 * @ingroup math
 */
template <typename T>
using SquareMatricesT2 = std::vector<SquareMatrixT2<T>>;
 
/**
 * Definition of a vector holding SquareMatrix2 objects.
 * @see SquareMatrix2
 * @ingroup math
 */
using SquareMatrices2 = std::vector<SquareMatrix2>;
 
/**
 * This class implements a 2x2 square matrix.
 * The four values are stored in a column aligned order with indices:
 * <pre>
 * | 0 2 |
 * | 1 3 |
 * </pre>
 * @tparam T Data type of matrix elements
 * @see SquareMatrix2, SquareMatrixF2, SquareMatrixD2.
 * @ingroup math
 */
template <typename T>
class SquareMatrixT2
{
  template <typename U> friend class SquareMatrixT2;
 
    public:
 
        /**
         * Definition of the used data type.
         */
        using Type = T;
 
    public:
 
        /**
         * Creates a new SquareMatrixT2 object with undefined elements.
         * Beware: This matrix is neither a zero nor an entity matrix!
         */
        inline SquareMatrixT2();
 
        /**
         * Copy constructor.
         * @param matrix The matrix to copy
         */
        SquareMatrixT2(const SquareMatrixT2<T>& matrix) = default;
 
        /**
         * Copy constructor for a matrix with difference element data type than T.
         * @param matrix The matrix to copy
         * @tparam U The element data type of the second matrix
         */
        template <typename U>
        inline explicit SquareMatrixT2(const SquareMatrixT2<U>& matrix);
 
        /**
         * Creates a new SquareMatrixT2 object.
         * @param setToIdentity Determines whether an identity matrix will be created, otherwise the matrix is initialized with zeros
         */
        inline explicit SquareMatrixT2(const bool setToIdentity);
 
        /**
         * Creates a new SquareMatrixT2 object by a given diagonal vector.
         * @param diagonal Diagonal vector for the new matrix
         */
        inline explicit SquareMatrixT2(const VectorT2<T>& diagonal);
 
        /**
         * Creates a new SquareMatrixT2 object by four elements of float type U.
         * @param arrayValues The four matrix elements defining the new matrix, must be valid
         * @tparam U The floating point type of the given elements
         */
        template <typename U>
        explicit SquareMatrixT2(const U* arrayValues);
 
        /**
         * Creates a new SquareMatrixT2 object by four elements.
         * @param arrayValues The four matrix elements defining the new matrix, must be valid
         */
        explicit SquareMatrixT2(const T* arrayValues);
 
        /**
         * Creates a new SquareMatrixT2 object by four elements.
         * @param arrayValues The four matrix elements defining the new matrix, must be valid
         * @param valuesRowAligned True, if the given values are stored in a row aligned order; False, if the values are stored in a column aligned order (which is the default case for this matrix)
         * @tparam U The floating point type of the given elements
         */
        template <typename U>
        SquareMatrixT2(const U* arrayValues, const bool valuesRowAligned);
 
        /**
         * Creates a new SquareMatrixT2 object by four elements.
         * @param arrayValues The four matrix elements defining the new matrix, must be valid
         * @param valuesRowAligned True, if the given values are stored in a row aligned order; False, if the values are stored in a column aligned order (which is the default case for this matrix)
         */
        SquareMatrixT2(const T* arrayValues, const bool valuesRowAligned);
 
        /**
         * Creates a 2x2 rotation matrix by 4 given matrix elements.
         * @param m00 Element of the first row and first column
         * @param m10 Element of the second row and first column
         * @param m01 Element of the first row and second column
         * @param m11 Element of the second row and second column
         */
        inline SquareMatrixT2(const T& m00, const T& m10, const T& m01, const T& m11);
 
        /**
         * Creates a covariance matrix by two eigen values and two corresponding eigen vectors.
         * @param eigenValue0 First eigen value
         * @param eigenValue1 Second eigen value
         * @param eigenVector0 First eigen vector
         * @param eigenVector1 Second eigen vector
         */
        SquareMatrixT2(const T eigenValue0, const T eigenValue1, const VectorT2<T>& eigenVector0, const VectorT2<T>& eigenVector1);
 
        /**
         * Returns the transposed of this matrix.
         * @return Transposed matrix
         */
        inline SquareMatrixT2<T> transposed() const;
 
        /**
         * Transposes the matrix.
         */
        inline void transpose();
 
        /**
         * Returns the inverted matrix of this matrix.
         * This matrix must not be singular.<br>
         * Beware: This function does not throw an exception if the matrix cannot be inverted.<br>
         * Thus, ensure that the matrix is invertible before calling this function.<br>
         * Even better: avoid the usage of this function and call invert() instead.<br>
         * In case, this matrix is not invertible, this matrix will be returned instead.
         * @return The inverted matrix
         * @see invert(), isSingular().
         */
        inline SquareMatrixT2<T> inverted() const;
 
        /**
         * Inverts this matrix in place.
         * @return True, if the matrix is not singular and could be inverted
         * @see inverted(), solve().
         */
        inline bool invert();
 
        /**
         * Inverts the matrix and returns the result as parameter.
         * @param invertedMatrix The resulting inverted matrix
         * @return True, if the matrix is not singular and could be inverted
         * @see inverted(), solve().
         */
        inline bool invert(SquareMatrixT2<T>& invertedMatrix) const;
 
        /**
         * Returns the determinant of the matrix.
         * @return Matrix determinant
         */
        inline T determinant() const;
 
        /**
         * Returns the trace of the matrix which is the sum of the diagonal elements.
         * @return Trace of the matrix
         */
        inline T trace() const;
 
        /**
         * Solve a simple 2x2 system of linear equations: Ax = b
         * Beware: The system of linear equations is assumed to be fully determined.
         * @param b The right-hand side vector
         * @param x The resulting solution vector
         * @return True, if the system could be solved
         * @see invert(), inverted().
         */
        inline bool solve(const VectorT2<T>& b, VectorT2<T>& x) const;
 
        /**
         * Sets the matrix to the identity matrix.
         */
        inline void toIdentity();
 
        /**
         * Sets the matrix to a zero matrix.
         * @see isNull();
         */
        inline void toNull();
 
        /**
         * Returns the x axis which is the first column of the matrix.
         * @return Vector with the first column
         */
        inline VectorT2<T> xAxis() const;
 
        /**
         * Returns the y axis which is the middle column of the matrix.
         * @return Vector with the middle column
         */
        inline VectorT2<T> yAxis() const;
 
        /**
         * Returns a 2D vector with values of the matrix diagonal.
         * @return Vector with diagonal values
         */
        inline VectorT2<T> diagonal() const;
 
        /**
         * Returns the norm of this matrix that is the sum of the absolute matrix elements.
         * @return Matrix norm
         */
        inline T norm() const;
 
        /**
         * Returns whether this matrix is a null matrix.
         * @return True, if so
         */
        inline bool isNull() const;
 
        /**
         * Returns whether this matrix is the identity matrix.
         * @return True, if so
         */
        inline bool isIdentity() const;
 
        /**
         * Returns whether this matrix is singular (and thus cannot be inverted).
         * A matrix is singular if the determinant of a matrix is 0.<br>
         * @return True, if so
         */
        inline bool isSingular() const;
 
        /**
         * Returns whether this matrix is symmetric.
         * @param epsilon The epsilon threshold to be used, with range [0, infinity)
         * @return True, if so
         */
        bool isSymmetric(const T epsilon = NumericT<T>::eps()) const;
 
        /**
         * Returns whether two matrices are almost identical up to a specified epsilon.
         * @param matrix Second matrix that will be checked
         * @param eps The epsilon threshold to be used, with range [0, infinity)
         * @return True, if so
         */
        inline bool isEqual(const SquareMatrixT2<T>& matrix, const T eps = NumericT<T>::eps()) const;
 
        /**
         * Performs an eigen value analysis.
         * @param eigenValue0 First eigen value
         * @param eigenValue1 Second eigen value
         * @param eigenVector0 First eigen vector
         * @param eigenVector1 Second eigen vector
         * @return True, if succeeded
         */
        bool eigenSystem(T& eigenValue0, T& eigenValue1, VectorT2<T>& eigenVector0, VectorT2<T>& eigenVector1) const;
 
        /**
         * Returns a pointer to the internal values.
         * @return Pointer to the internal values
         */
        inline const T* data() const;
 
        /**
         * Returns a pointer to the internal values.
         * @return Pointer to the internal values
         */
        inline T* data();
 
        /**
         * Copies the elements of this matrix to an array with floating point values of type U.
         * @param arrayValues Array with 4 floating point values of type U receiving the elements of this matrix
         * @param columnAligned True, if the target elements are column aligned, false to target row aligned elements
         * @tparam U Floating point type
         */
        template <typename U>
        inline void copyElements(U* arrayValues, const bool columnAligned = true) const;
 
        /**
         * Copies the elements of this matrix to an array with floating point values of type T.
         * @param arrayValues Array with 4 floating point values  of type T receiving the elements of this matrix
         * @param columnAligned True, if the target elements are column aligned, false to target row aligned elements
         */
        inline void copyElements(T* arrayValues, const bool columnAligned = true) const;
 
        /**
         * Default copy assignment operator.
         * @return Reference to this object
         */
        SquareMatrixT2<T>& operator=(const SquareMatrixT2<T>&) = default;
 
        /**
         * Returns whether two matrices are identical up to a small epsilon.
         * @param matrix Right operand
         * @return True, if so
         */
        inline bool operator==(const SquareMatrixT2<T>& matrix) const;
 
        /**
         * Returns whether two matrices are not identical up to a small epsilon.
         * @param matrix Right operand
         * @return True, if so
         */
        inline bool operator!=(const SquareMatrixT2<T>& matrix) const;
 
        /**
         * Adds two matrices.
         * @param matrix Right operand
         * @return Sum matrix
         */
        inline SquareMatrixT2<T> operator+(const SquareMatrixT2<T>& matrix) const;
 
        /**
         * Adds and assigns two matrices.
         * @param matrix Right operand
         * @return Reference to this object
         */
        inline SquareMatrixT2<T>& operator+=(const SquareMatrixT2<T>& matrix);
 
        /**
         * Subtracts two matrices.
         * @param matrix Right operand
         * @return Difference matrix
         */
        inline SquareMatrixT2<T> operator-(const SquareMatrixT2<T>& matrix) const;
 
        /**
         * Subtracts and assigns two matrices.
         * @param matrix Right operand
         * @return Reference to this object
         */
        inline SquareMatrixT2<T>& operator-=(const SquareMatrixT2<T>& matrix);
 
        /**
         * Returns the negative matrix of this matrix (all matrix elements are multiplied by -1).
         * @return Resulting negative matrix
         */
        inline SquareMatrixT2<T> operator-() const;
 
        /**
         * Multiplies two matrices.
         * @param matrix Right operand
         * @return Product matrix
         */
        inline SquareMatrixT2<T> operator*(const SquareMatrixT2<T>& matrix) const;
 
        /**
         * Multiplies and assigns two matrices.
         * @param matrix Right operand
         * @return Reference to this object
         */
        inline SquareMatrixT2<T>& operator*=(const SquareMatrixT2<T>& matrix);
 
        /**
         * Multiply operator for a 2D vector.
         * @param vector Right operand
         * @return Resulting 2D vector
         */
        inline VectorT2<T> operator*(const VectorT2<T>& vector) const;
 
        /**
         * Multiplies this matrix with a scalar value.
         * @param value Right operand
         * @return Resulting matrix
         */
        inline SquareMatrixT2<T> operator*(const T value) const;
 
        /**
         * Multiplies and assigns this matrix with a scalar value.
         * @param value right operand
         * @return Reference to this object
         */
        inline SquareMatrixT2<T>& operator*=(const T value);
 
        /**
         * Element operator.
         * Beware: No range check will be done!
         * @param index Index of the element to return [0, 4]
         * @return Specified element
         */
        inline T operator[](const unsigned int index) const;
 
        /**
         * Element operator.
         * Beware: No range check will be done!
         * @param index Index of the element to return [0, 4]
         * @return Specified element
         */
        inline T& operator[](const unsigned int index);
 
        /**
         * Element operator.
         * Beware: No range check will be done!
         * @param row Row of the element to return [0, 1]
         * @param column Column of the element to return [0, 1]
         * @return Specified element
         */
        inline T operator()(const unsigned int row, const unsigned int column) const;
 
        /**
         * Element operator.
         * Beware: No range check will be done!
         * @param row Row of the element to return [0, 1]
         * @param column Column of the element to return [0, 1]
         * @return Specified element
         */
        inline T& operator()(const unsigned int row, const unsigned int column);
 
        /**
         * Element operator.
         * Beware: No range check will be done!
         * @param index Index of the element to return [0, 8]
         * @return Specified element
         */
        inline T operator()(const unsigned int index) const;
 
        /**
         * Element operator.
         * Beware: No range check will be done!
         * @param index Index of the element to return [0, 8]
         * @return Specified element
         */
        inline T& operator()(const unsigned int index);
 
        /**
         * Access operator.
         * @return Pointer to the internal values
         */
        inline const T* operator()() const;
 
        /**
         * Access operator.
         * @return Pointer to the internal values
         */
        inline T* operator()();
 
        /**
         * Hash function.
         * @param matrix The matrix for which the hash value will be determined
         * @return The resulting hash value
         */
        inline size_t operator()(const SquareMatrixT2<T>& matrix) const;
 
        /**
         * Returns the number of elements this matrix has.
         * @return The number of elements, always 4
         */
        static inline size_t elements();
 
        /**
         * Converts matrices with specific data type to matrices with different data type.
         * @param matrices The matrices to convert
         * @return The converted matrices
         * @tparam U The element data type of the matrices to convert
         */
        template <typename U>
        static inline std::vector< SquareMatrixT2<T> > matrices2matrices(const std::vector< SquareMatrixT2<U> >& matrices);
 
        /**
         * Converts matrices with specific data type to matrices with different data type.
         * @param matrices The matrices to convert
         * @param size The number of matrices to convert
         * @return The converted matrices
         * @tparam U The element data type of the matrices to convert
         */
        template <typename U>
        static inline std::vector< SquareMatrixT2<T> > matrices2matrices(const SquareMatrixT2<U>* matrices, const size_t size);
 
    protected:
 
        /// The four values of the matrix.
        T values_[4];
};
 
template <typename T>
inline SquareMatrixT2<T>::SquareMatrixT2()
{
    // nothing to do here
}
 
template <typename T>
template <typename U>
inline SquareMatrixT2<T>::SquareMatrixT2(const SquareMatrixT2<U>& matrix)
{
    values_[0] = T(matrix.values_[0]);
    values_[1] = T(matrix.values_[1]);
    values_[2] = T(matrix.values_[2]);
    values_[3] = T(matrix.values_[3]);
}
 
template <typename T>
inline SquareMatrixT2<T>::SquareMatrixT2(const bool setToIdentity)
{
    if (setToIdentity)
    {
        values_[0] = T(1.0);
        values_[1] = T(0.0);
        values_[2] = T(0.0);
        values_[3] = T(1.0);
    }
    else
    {
        values_[0] = T(0.0);
        values_[1] = T(0.0);
        values_[2] = T(0.0);
        values_[3] = T(0.0);
    }
}
 
template <typename T>
inline SquareMatrixT2<T>::SquareMatrixT2(const VectorT2<T>& diagonal)
{
    values_[0] = diagonal[0];
    values_[1] = T(0.0);
    values_[2] = T(0.0);
    values_[3] = diagonal[1];
}
 
template <typename T>
template <typename U>
SquareMatrixT2<T>::SquareMatrixT2(const U* arrayValues)
{
    ocean_assert(arrayValues);
 
    for (unsigned int n = 0u; n < 4u; ++n)
    {
        values_[n] = T(arrayValues[n]);
    }
}
 
template <typename T>
SquareMatrixT2<T>::SquareMatrixT2(const T* arrayValues)
{
    ocean_assert(arrayValues);
    memcpy(values_, arrayValues, sizeof(T) * 4);
}
 
template <typename T>
template <typename U>
SquareMatrixT2<T>::SquareMatrixT2(const U* arrayValues, const bool valuesRowAligned)
{
    ocean_assert(arrayValues);
 
    if (valuesRowAligned)
    {
        values_[0] = T(arrayValues[0]);
        values_[1] = T(arrayValues[2]);
        values_[2] = T(arrayValues[1]);
        values_[3] = T(arrayValues[3]);
 
    }
    else
    {
        for (unsigned int n = 0u; n < 4u; ++n)
        {
            values_[n] = T(arrayValues[n]);
        }
    }
}
 
template <typename T>
SquareMatrixT2<T>::SquareMatrixT2(const T* arrayValues, const bool valuesRowAligned)
{
    ocean_assert(arrayValues);
 
    if (valuesRowAligned)
    {
        values_[0] = arrayValues[0];
        values_[1] = arrayValues[2];
        values_[2] = arrayValues[1];
        values_[3] = arrayValues[3];
    }
    else
    {
        memcpy(values_, arrayValues, sizeof(T) * 4);
    }
}
 
template <typename T>
inline SquareMatrixT2<T>::SquareMatrixT2(const T& m00, const T& m10, const T& m01, const T& m11)
{
    values_[0] = m00;
    values_[1] = m10;
 
    values_[2] = m01;
    values_[3] = m11;
}
 
template <typename T>
SquareMatrixT2<T>::SquareMatrixT2(const T eigenValue0, const T eigenValue1, const VectorT2<T>& eigenVector0, const VectorT2<T>& eigenVector1)
{
    ocean_assert(eigenVector0.isUnit());
    ocean_assert(eigenVector1.isUnit());
 
    const T determinant = eigenVector0.x() * eigenVector1.y() - eigenVector1.x() * eigenVector0.y();
    ocean_assert(NumericT<T>::isNotEqualEps(determinant));
 
    values_[0] = (eigenVector0.x() * eigenValue0 * eigenVector1.y() - eigenVector0.y() * eigenValue1 * eigenVector1.x()) / determinant;
    values_[1] = (eigenValue0 - eigenValue1) * eigenVector0.y() * eigenVector1.y() / determinant;
    values_[2] = (eigenValue1 - eigenValue0) * eigenVector0.x() * eigenVector1.x() / determinant;
    values_[3] = (eigenVector0.x() * eigenValue1 * eigenVector1.y() - eigenVector0.y() * eigenValue0 * eigenVector1.x()) / determinant;
}
 
template <typename T>
inline SquareMatrixT2<T> SquareMatrixT2<T>::transposed() const
{
    return SquareMatrixT2<T>(values_[0], values_[2], values_[1], values_[3]);
}
 
template <typename T>
inline void SquareMatrixT2<T>::transpose()
{
    const T tmp = values_[1];
    values_[1] = values_[2];
    values_[2] = tmp;
}
 
template <typename T>
inline SquareMatrixT2<T> SquareMatrixT2<T>::inverted() const
{
    SquareMatrixT2<T> result;
 
    if (!invert(result))
    {
        ocean_assert(false && "Could not invert the matrix.");
        return *this;
    }
 
    return result;
}
 
template <typename T>
inline bool SquareMatrixT2<T>::invert()
{
    const T det = determinant();
    if (NumericT<T>::isEqualEps(det))
    {
        return false;
    }
 
    const T factor = T(1.0) / det;
 
    *this = SquareMatrixT2<T>(values_[3] * factor, -values_[1] * factor, -values_[2] * factor, values_[0] * factor);
 
    return true;
}
 
template <typename T>
inline bool SquareMatrixT2<T>::invert(SquareMatrixT2<T>& invertedMatrix) const
{
    const T det = determinant();
    if (NumericT<T>::isEqualEps(det))
    {
        return false;
    }
 
    const T factor = T(1.0) / det;
 
    invertedMatrix = SquareMatrixT2<T>(values_[3] * factor, -values_[1] * factor, -values_[2] * factor, values_[0] * factor);
 
#ifdef OCEAN_INTENSIVE_DEBUG
    if (!std::is_same<T, float>::value)
    {
        const SquareMatrixT2<T> test(*this * invertedMatrix);
        const SquareMatrixT2<T> entity(true);
 
        T sqrDistance = T(0);
        for (unsigned int n = 0; n < 4u; ++n)
        {
            sqrDistance += NumericT<T>::sqr(test[n] - entity[n]);
        }
 
        const T distance = NumericT<T>::sqrt(sqrDistance * T(0.25));
 
        if (NumericT<T>::isWeakEqualEps(distance) == false)
        {
            T absolusteAverageEnergy = 0;
            for (unsigned int n = 0u; n < 4u; ++n)
            {
                absolusteAverageEnergy += NumericT<T>::abs(values_[n]);
            }
            absolusteAverageEnergy *= T(0.25);
 
            // we expect/accept for each magnitude (larger than 1) a zero-inaccuracy of one magnitude (and we again comare it with the weak eps)
 
            if (absolusteAverageEnergy <= 1)
            {
                ocean_assert_accuracy(!"This should never happen!");
            }
            else
            {
                const T adjustedDistance = distance / absolusteAverageEnergy;
                ocean_assert_accuracy(NumericT<T>::isWeakEqualEps(adjustedDistance));
            }
        }
    }
#endif // OCEAN_DEBUG
 
    return true;
}
 
template <typename T>
inline T SquareMatrixT2<T>::determinant() const
{
    return values_[0] * values_[3] - values_[1] * values_[2];
}
 
template <typename T>
inline T SquareMatrixT2<T>::trace() const
{
    return values_[0] + values_[3];
}
 
template <typename T>
inline bool SquareMatrixT2<T>::solve(const VectorT2<T>& b, VectorT2<T>& x) const
{
    const T determinant = (values_[0] * values_[3]) - (values_[1] * values_[2]);
 
    if (NumericT<T>::isNotEqualEps(determinant))
    {
        x[0] = (values_[3] * b[0] - values_[2] * b[1]) / determinant;
        x[1] = (values_[0] * b[1] - values_[1] * b[0]) / determinant;
 
        return true;
    }
 
    return false;
}
 
template <typename T>
inline void SquareMatrixT2<T>::toIdentity()
{
    values_[0] = T(1.0);
    values_[1] = T(0.0);
    values_[2] = T(0.0);
    values_[3] = T(1.0);
}
 
template <typename T>
inline void SquareMatrixT2<T>::toNull()
{
    values_[0] = T(0.0);
    values_[1] = T(0.0);
    values_[2] = T(0.0);
    values_[3] = T(0.0);
}
 
template <typename T>
inline VectorT2<T> SquareMatrixT2<T>::xAxis() const
{
    return VectorT2<T>(values_[0], values_[1]);
}
 
template <typename T>
inline VectorT2<T> SquareMatrixT2<T>::yAxis() const
{
    return VectorT2<T>(values_[2], values_[3]);
}
 
template <typename T>
inline VectorT2<T> SquareMatrixT2<T>::diagonal() const
{
    return VectorT2<T>(values_[0], values_[3]);
}
 
template <typename T>
inline T SquareMatrixT2<T>::norm() const
{
    return NumericT<T>::abs(values_[0]) + NumericT<T>::abs(values_[1]) + NumericT<T>::abs(values_[2]) + NumericT<T>::abs(values_[3]);
}
 
template <typename T>
inline bool SquareMatrixT2<T>::isNull() const
{
    return NumericT<T>::isEqualEps(values_[0]) && NumericT<T>::isEqualEps(values_[1]) && NumericT<T>::isEqualEps(values_[2]) && NumericT<T>::isEqualEps(values_[3]);
}
 
template <typename T>
inline bool SquareMatrixT2<T>::isIdentity() const
{
    return NumericT<T>::isEqual(values_[0], 1) && NumericT<T>::isEqualEps(values_[1]) && NumericT<T>::isEqualEps(values_[2]) && NumericT<T>::isEqual(values_[3], 1);
}
 
template <typename T>
inline bool SquareMatrixT2<T>::isSingular() const
{
    return NumericT<T>::isEqualEps(determinant());
}
 
template <typename T>
inline bool SquareMatrixT2<T>::isSymmetric(const T epsilon) const
{
    ocean_assert(epsilon >= T(0));
 
    return NumericT<T>::isEqual(values_[1], values_[2], epsilon);
}
 
template <typename T>
inline bool SquareMatrixT2<T>::isEqual(const SquareMatrixT2<T>& matrix, const T eps) const
{
    return NumericT<T>::isEqual(values_[0], matrix.values_[0], eps) && NumericT<T>::isEqual(values_[1], matrix.values_[1], eps)
            && NumericT<T>::isEqual(values_[2], matrix.values_[2], eps) && NumericT<T>::isEqual(values_[3], matrix.values_[3], eps);
}
 
template <typename T>
inline const T* SquareMatrixT2<T>::data() const
{
    return values_;
}
 
template <typename T>
inline T* SquareMatrixT2<T>::data()
{
    return values_;
}
 
template <typename T>
template <typename U>
inline void SquareMatrixT2<T>::copyElements(U* arrayValues, const bool columnAligned) const
{
    ocean_assert(arrayValues);
 
    if (columnAligned)
    {
        arrayValues[0] = U(values_[0]);
        arrayValues[1] = U(values_[1]);
        arrayValues[2] = U(values_[2]);
        arrayValues[3] = U(values_[3]);
    }
    else
    {
        arrayValues[0] = U(values_[0]);
        arrayValues[1] = U(values_[2]);
        arrayValues[2] = U(values_[1]);
        arrayValues[3] = U(values_[3]);
    }
}
 
template <typename T>
inline void SquareMatrixT2<T>::copyElements(T* arrayValues, const bool columnAligned) const
{
    ocean_assert(arrayValues);
 
    if (columnAligned)
    {
        arrayValues[0] = values_[0];
        arrayValues[1] = values_[1];
        arrayValues[2] = values_[2];
        arrayValues[3] = values_[3];
    }
    else
    {
        arrayValues[0] = values_[0];
        arrayValues[1] = values_[2];
        arrayValues[2] = values_[1];
        arrayValues[3] = values_[3];
    }
}
 
template <typename T>
inline bool SquareMatrixT2<T>::operator==(const SquareMatrixT2<T>& matrix) const
{
    return isEqual(matrix);
}
 
template <typename T>
inline bool SquareMatrixT2<T>::operator!=(const SquareMatrixT2<T>& matrix) const
{
    return !(*this == matrix);
}
 
template <typename T>
inline SquareMatrixT2<T> SquareMatrixT2<T>::operator+(const SquareMatrixT2<T>& matrix) const
{
    return SquareMatrixT2<T>(values_[0] + matrix.values_[0], values_[1] + matrix.values_[1], values_[2] + matrix.values_[2], values_[3] + matrix.values_[3]);
}
 
template <typename T>
inline SquareMatrixT2<T>& SquareMatrixT2<T>::operator+=(const SquareMatrixT2<T>& matrix)
{
    values_[0] += matrix.values_[0];
    values_[1] += matrix.values_[1];
    values_[2] += matrix.values_[2];
    values_[3] += matrix.values_[3];
 
    return *this;
}
 
template <typename T>
inline SquareMatrixT2<T> SquareMatrixT2<T>::operator-(const SquareMatrixT2<T>& matrix) const
{
    return SquareMatrixT2<T>(values_[0] - matrix.values_[0], values_[1] - matrix.values_[1], values_[2] - matrix.values_[2], values_[3] - matrix.values_[3]);
}
 
template <typename T>
inline SquareMatrixT2<T>& SquareMatrixT2<T>::operator-=(const SquareMatrixT2<T>& matrix)
{
    values_[0] -= matrix.values_[0];
    values_[1] -= matrix.values_[1];
    values_[2] -= matrix.values_[2];
    values_[3] -= matrix.values_[3];
 
    return *this;
}
 
template <typename T>
inline SquareMatrixT2<T> SquareMatrixT2<T>::operator-() const
{
    SquareMatrixT2<T> result;
 
    result.values_[ 0] = -values_[ 0];
    result.values_[ 1] = -values_[ 1];
    result.values_[ 2] = -values_[ 2];
    result.values_[ 3] = -values_[ 3];
 
    return result;
}
 
template <typename T>
inline SquareMatrixT2<T> SquareMatrixT2<T>::operator*(const SquareMatrixT2<T>& matrix) const
{
    return SquareMatrixT2<T>(values_[0] * matrix.values_[0] + values_[2] * matrix.values_[1],
                            values_[1] * matrix.values_[0] + values_[3] * matrix.values_[1],
                            values_[0] * matrix.values_[2] + values_[2] * matrix.values_[3],
                            values_[1] * matrix.values_[2] + values_[3] * matrix.values_[3]);
}
 
template <typename T>
inline SquareMatrixT2<T>& SquareMatrixT2<T>::operator*=(const SquareMatrixT2<T>& matrix)
{
    *this = *this * matrix;
    return *this;
}
 
template <typename T>
inline VectorT2<T> SquareMatrixT2<T>::operator*(const VectorT2<T>& vector) const
{
    return VectorT2<T>(values_[0] * vector[0] + values_[2] * vector[1],
                        values_[1] * vector[0] + values_[3] * vector[1]);
}
 
template <typename T>
inline SquareMatrixT2<T> SquareMatrixT2<T>::operator*(const T value) const
{
    return SquareMatrixT2<T>(values_[0] * value, values_[1] * value, values_[2] * value, values_[3] * value);
}
 
template <typename T>
inline SquareMatrixT2<T>& SquareMatrixT2<T>::operator*=(const T value)
{
    values_[0] *= value;
    values_[1] *= value;
    values_[2] *= value;
    values_[3] *= value;
 
    return *this;
}
 
template <typename T>
inline T SquareMatrixT2<T>::operator[](const unsigned int index) const
{
    ocean_assert(index < 4u);
    return values_[index];
}
 
template <typename T>
inline T& SquareMatrixT2<T>::operator[](const unsigned int index)
{
    ocean_assert(index < 4u);
    return values_[index];
}
 
template <typename T>
inline T SquareMatrixT2<T>::operator()(const unsigned int row, const unsigned int column) const
{
    ocean_assert(row < 2u && column < 2u);
    return values_[column * 2u + row];
}
 
template <typename T>
inline T& SquareMatrixT2<T>::operator()(const unsigned int row, const unsigned int column)
{
    ocean_assert(row < 2u && column < 2u);
    return values_[column * 2u + row];
}
 
template <typename T>
inline T SquareMatrixT2<T>::operator()(const unsigned int index) const
{
    ocean_assert(index < 4u);
    return values_[index];
}
 
template <typename T>
inline T& SquareMatrixT2<T>::operator()(const unsigned int index)
{
    ocean_assert(index < 4u);
    return values_[index];
}
 
template <typename T>
inline const T* SquareMatrixT2<T>::operator()() const
{
    return values_;
}
 
template <typename T>
inline T* SquareMatrixT2<T>::operator()()
{
    return values_;
}
 
template <typename T>
inline size_t SquareMatrixT2<T>::operator()(const SquareMatrixT2<T>& matrix) const
{
    size_t seed = std::hash<T>{}(matrix.values_[0]);
 
    for (unsigned int n = 1u; n < 4u; ++n)
    {
        seed ^= std::hash<T>{}(matrix.values_[n]) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
    }
 
    return seed;
}
 
template <typename T>
inline size_t SquareMatrixT2<T>::elements()
{
    return 4;
}
 
template <typename T>
bool SquareMatrixT2<T>::eigenSystem(T& eigenValue0, T& eigenValue1, VectorT2<T>& eigenVector0, VectorT2<T>& eigenVector1) const
{
    if (isNull())
    {
        return false;
    }
 
    const T tr = trace();
    const T det = determinant();
 
    if (!EquationT<T>::solveQuadratic(T(1.0), -tr, det, eigenValue0, eigenValue1))
    {
        return false;
    }
 
    if (eigenValue0 < eigenValue1)
    {
        std::swap(eigenValue0, eigenValue1);
    }
 
    if (NumericT<T>::isNotEqualEps(values_[2]))
    {
        const T factor = T(1.0) / values_[2];
        eigenVector0 = VectorT2<T>(1, (eigenValue0 - values_[0]) * factor);
        eigenVector1 = VectorT2<T>(1, (eigenValue1 - values_[0]) * factor);
    }
    else if (NumericT<T>::isNotEqualEps(values_[1]))
    {
        const T factor = T(1.0) / values_[1];
 
        eigenVector0 = VectorT2<T>((eigenValue0 - values_[3]) * factor, T(1.0));
        eigenVector1 = VectorT2<T>((eigenValue1 - values_[3]) * factor, T(1.0));
    }
    else
    {
        if (NumericT<T>::isNotEqual(eigenValue0, values_[3]))
        {
            eigenVector0 = VectorT2<T>(1, values_[1] / (eigenValue0 - values_[3]));
        }
        else
        {
            if (NumericT<T>::isEqual(eigenValue0, values_[0]))
            {
                eigenVector0 = VectorT2<T>(1, 0);
            }
            else
            {
                eigenVector0 = VectorT2<T>(values_[2] / (eigenValue0 - values_[0]), T(1.0));
            }
        }
 
        if (NumericT<T>::isNotEqual(values_[3], eigenValue1))
        {
            eigenVector1 = VectorT2<T>(1, values_[1] / (eigenValue1 - values_[3]));
        }
        else
        {
            if (NumericT<T>::isEqual(eigenValue1, values_[0]))
            {
                eigenVector1 = VectorT2<T>(0, 1);
            }
            else
            {
                eigenVector1 = VectorT2<T>(values_[2] / (eigenValue1 - values_[0]), T(1.0));
            }
        }
    }
 
    eigenVector0.normalize();
    eigenVector1.normalize();
 
    ocean_assert((std::is_same<T, float>::value) || (*this * eigenVector0).isEqual(eigenVector0 * eigenValue0, NumericT<T>::weakEps()));
    ocean_assert((std::is_same<T, float>::value) || (*this * eigenVector1).isEqual(eigenVector1 * eigenValue1, NumericT<T>::weakEps()));
 
    return true;
}
 
template <typename T>
template <typename U>
inline std::vector< SquareMatrixT2<T> > SquareMatrixT2<T>::matrices2matrices(const std::vector< SquareMatrixT2<U> >& matrices)
{
    std::vector< SquareMatrixT2<T> > result;
    result.reserve(matrices.size());
 
    for (typename std::vector< SquareMatrixT2<U> >::const_iterator i = matrices.begin(); i != matrices.end(); ++i)
    {
        result.push_back(SquareMatrixT2<T>(*i));
    }
 
    return result;
}
 
template <>
template <>
inline std::vector< SquareMatrixT2<float> > SquareMatrixT2<float>::matrices2matrices(const std::vector< SquareMatrixT2<float> >& matrices)
{
    return matrices;
}
 
template <>
template <>
inline std::vector< SquareMatrixT2<double> > SquareMatrixT2<double>::matrices2matrices(const std::vector< SquareMatrixT2<double> >& matrices)
{
    return matrices;
}
 
template <typename T>
template <typename U>
inline std::vector< SquareMatrixT2<T> > SquareMatrixT2<T>::matrices2matrices(const SquareMatrixT2<U>* matrices, const size_t size)
{
    std::vector< SquareMatrixT2<T> > result;
    result.reserve(size);
 
    for (size_t n = 0; n < size; ++n)
    {
        result.push_back(SquareMatrixT2<T>(matrices[n]));
    }
 
    return result;
}
 
template <typename T>
std::ostream& operator<<(std::ostream& stream, const SquareMatrixT2<T>& matrix)
{
    stream << "|" << matrix(0, 0) << ", " << matrix(0, 1) << "|" << std::endl;
    stream << "|" << matrix(1, 0) << ", " << matrix(1, 1) << "|";
 
    return stream;
}
 
template <bool tActive, typename T>
MessageObject<tActive>& operator<<(MessageObject<tActive>& messageObject, const SquareMatrixT2<T>& matrix)
{
    return messageObject << "|" << matrix(0, 0) << ", " << matrix(0, 1) << "|\n|" << matrix(1, 0) << ", " << matrix(1, 1) << "|";
}
 
template <bool tActive, typename T>
MessageObject<tActive>& operator<<(MessageObject<tActive>&& messageObject, const SquareMatrixT2<T>& matrix)
{
    return messageObject << "|" << matrix(0, 0) << ", " << matrix(0, 1) << "|\n|" << matrix(1, 0) << ", " << matrix(1, 1) << "|";
}
 
}
 
#endif // META_OCEAN_MATH_SQUARE_MATRIX_2_H