ImplementationDetails/NormalMode.hpp

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/**
 * @file
 * Implements functionality in the `OpenMPCD::NormalMode` namespace.
 */
 
#ifndef OPENMPCD_IMPLEMENTATIONDETAILS_NORMALMODE_HPP
#define OPENMPCD_IMPLEMENTATIONDETAILS_NORMALMODE_HPP
 
#include <OpenMPCD/Exceptions.hpp>
#include <OpenMPCD/OPENMPCD_DEBUG_ASSERT.hpp>
 
#include <boost/math/constants/constants.hpp>
#include <boost/static_assert.hpp>
#include <boost/type_traits/is_floating_point.hpp>
 
namespace OpenMPCD
{
namespace NormalMode
{
 
template<typename T>
const Vector3D<T> computeNormalCoordinate(
    const unsigned int i, const Vector3D<T>* const vectors,
    const std::size_t N, const T shift)
{
    BOOST_STATIC_ASSERT(boost::is_floating_point<T>::value);
        //non-floating-point `T` is probably a mistake
 
    OPENMPCD_DEBUG_ASSERT_EXCEPTIONTYPE(vectors, NULLPointerException);
    OPENMPCD_DEBUG_ASSERT_EXCEPTIONTYPE(N != 0, InvalidArgumentException);
    OPENMPCD_DEBUG_ASSERT_EXCEPTIONTYPE(i <= N, InvalidArgumentException);
 
    Vector3D<T> ret(0, 0, 0);
 
    const T pi = boost::math::constants::pi<T>();
    const T argPart = T(i) * pi / T(N);
    for(std::size_t n = 1; n <= N; ++n)
        ret += vectors[n - 1] * cos(argPart * (n + shift));
 
    return ret / T(N);
}
 
} //namespace NormalMode
} //namespace OpenMPCD
 
#endif //OPENMPCD_IMPLEMENTATIONDETAILS_NORMALMODE_HPP