#include <NekFFTW.h>

Inheritance diagram for Nektar::LibUtilities::NekFFTW:

Public Member Functions
	NekFFTW (int N)

	~NekFFTW () override

Public Member Functions inherited from Nektar::LibUtilities::NektarFFT
	NektarFFT (int N)
	Initialises NektarFFT class members. More...

virtual	~NektarFFT ()

void	FFTFwdTrans (Array< OneD, NekDouble > &phy, Array< OneD, NekDouble > &coef)

void	FFTBwdTrans (Array< OneD, NekDouble > &coef, Array< OneD, NekDouble > &phys)

Static Public Member Functions
static NektarFFTSharedPtr	create (int N)
	Creates an instance of this class. More...

Static Public Attributes
static std::string	className
	Name of class. More...

Protected Member Functions
void	Reshuffle_FFTW2Nek (Array< OneD, NekDouble > &coef)

void	Reshuffle_Nek2FFTW (Array< OneD, NekDouble > &coef)

void	v_FFTFwdTrans (Array< OneD, NekDouble > &inarray, Array< OneD, NekDouble > &outarray) override

void	v_FFTBwdTrans (Array< OneD, NekDouble > &inarray, Array< OneD, NekDouble > &outarray) override

virtual void	v_FFTFwdTrans (Array< OneD, NekDouble > &phys, Array< OneD, NekDouble > &coef)

virtual void	v_FFTBwdTrans (Array< OneD, NekDouble > &coef, Array< OneD, NekDouble > &phys)

Protected Attributes
Array< OneD, NekDouble >	m_FFTW_w

Array< OneD, NekDouble >	m_FFTW_w_inv

Array< OneD, NekDouble >	m_phys

Array< OneD, NekDouble >	m_coef

Array< OneD, NekDouble >	m_wsp

fftw_plan	m_plan_backward

fftw_plan	m_plan_forward

Additional Inherited Members
Public Attributes inherited from Nektar::LibUtilities::NektarFFT
int	m_N

Detailed Description

Definition at line 59 of file NekFFTW.h.

Constructor & Destructor Documentation

◆ NekFFTW()

Nektar::LibUtilities::NekFFTW::NekFFTW ( int N )

Definition at line 44 of file NekFFTW.cpp.

                      : NektarFFT(N)
{
    m_wsp  = Array<OneD, NekDouble>(m_N);
    m_phys = Array<OneD, NekDouble>(m_N);
    m_coef = Array<OneD, NekDouble>(m_N);
 
    m_plan_forward =
        fftw_plan_r2r_1d(m_N, &m_phys[0], &m_coef[0], FFTW_R2HC, FFTW_ESTIMATE);
    m_plan_backward =
        fftw_plan_r2r_1d(m_N, &m_coef[0], &m_phys[0], FFTW_HC2R, FFTW_ESTIMATE);
 
    m_FFTW_w     = Array<OneD, NekDouble>(m_N);
    m_FFTW_w_inv = Array<OneD, NekDouble>(m_N);
 
    m_FFTW_w[0] = 1.0 / (NekDouble)m_N;
    m_FFTW_w[1] = 0.0;
 
    m_FFTW_w_inv[0] = m_N;
    m_FFTW_w_inv[1] = 0.0;
 
    for (int i = 2; i < m_N; i++)
    {
        m_FFTW_w[i]     = m_FFTW_w[0] * 2;
        m_FFTW_w_inv[i] = m_FFTW_w_inv[0] / 2;
    }
}

References m_coef, m_FFTW_w, m_FFTW_w_inv, Nektar::LibUtilities::NektarFFT::m_N, m_phys, m_plan_backward, m_plan_forward, and m_wsp.

◆ ~NekFFTW()

Nektar::LibUtilities::NekFFTW::~NekFFTW ( )

override

Definition at line 72 of file NekFFTW.cpp.

73{

74}

Member Function Documentation

◆ create()

static NektarFFTSharedPtr Nektar::LibUtilities::NekFFTW::create ( int N )

inlinestatic

Creates an instance of this class.

Definition at line 63 of file NekFFTW.h.

    {
        return MemoryManager<NekFFTW>::AllocateSharedPtr(N);
    }

References Nektar::MemoryManager< DataType >::AllocateSharedPtr().

◆ Reshuffle_FFTW2Nek()

void Nektar::LibUtilities::NekFFTW::Reshuffle_FFTW2Nek ( Array< OneD, NekDouble > & coef )

protected

Reshuffling routines to put the coefficients in Nektar++/FFTW format. The routines take as an input the number of points N, the vector of coeffcients and the vector containing the weights of the numerical integration. The routines modify directly the coef vector.

Definition at line 103 of file NekFFTW.cpp.

{
    int halfN = m_N / 2;
 
    m_wsp[1] = coef[halfN];
 
    Vmath::Vcopy(halfN, coef, 1, m_wsp, 2);
 
    for (int i = 0; i < (halfN - 1); i++)
    {
        m_wsp[(m_N - 1) - 2 * i] = coef[halfN + 1 + i];
    }
 
    Vmath::Vmul(m_N, m_wsp, 1, m_FFTW_w, 1, coef, 1);
 
    return;
}

References m_FFTW_w, Nektar::LibUtilities::NektarFFT::m_N, m_wsp, Vmath::Vcopy(), and Vmath::Vmul().

Referenced by v_FFTFwdTrans().

◆ Reshuffle_Nek2FFTW()

void Nektar::LibUtilities::NekFFTW::Reshuffle_Nek2FFTW ( Array< OneD, NekDouble > & coef )

protected

Definition at line 122 of file NekFFTW.cpp.

{
    int halfN = m_N / 2;
 
    Vmath::Vmul(m_N, coef, 1, m_FFTW_w_inv, 1, coef, 1);
 
    m_wsp[halfN] = coef[1];
 
    Vmath::Vcopy(halfN, coef, 2, m_wsp, 1);
 
    for (int i = 0; i < (halfN - 1); i++)
    {
        m_wsp[halfN + 1 + i] = coef[(m_N - 1) - 2 * i];
    }
 
    Vmath::Smul(m_N, 1.0 / m_N, m_wsp, 1, coef, 1);
 
    return;
}

References m_FFTW_w_inv, Nektar::LibUtilities::NektarFFT::m_N, m_wsp, Vmath::Smul(), Vmath::Vcopy(), and Vmath::Vmul().

Referenced by v_FFTBwdTrans().

◆ v_FFTBwdTrans()

void Nektar::LibUtilities::NekFFTW::v_FFTBwdTrans	(	Array< OneD, NekDouble > &	inarray,
		Array< OneD, NekDouble > &	outarray
	)

overrideprotectedvirtual

Reimplemented from Nektar::LibUtilities::NektarFFT.

Definition at line 90 of file NekFFTW.cpp.

{
    Vmath::Vcopy(m_N, inarray, 1, m_coef, 1);
 
    Reshuffle_Nek2FFTW(m_coef);
 
    fftw_execute(m_plan_backward);
 
    Vmath::Vcopy(m_N, m_phys, 1, outarray, 1);
}

References m_coef, Nektar::LibUtilities::NektarFFT::m_N, m_phys, m_plan_backward, Reshuffle_Nek2FFTW(), and Vmath::Vcopy().

◆ v_FFTFwdTrans()

void Nektar::LibUtilities::NekFFTW::v_FFTFwdTrans	(	Array< OneD, NekDouble > &	inarray,
		Array< OneD, NekDouble > &	outarray
	)

overrideprotectedvirtual

Reimplemented from Nektar::LibUtilities::NektarFFT.

Definition at line 77 of file NekFFTW.cpp.

{
    Vmath::Vcopy(m_N, inarray, 1, m_phys, 1);
 
    fftw_execute(m_plan_forward);
 
    Reshuffle_FFTW2Nek(m_coef);
 
    Vmath::Vcopy(m_N, m_coef, 1, outarray, 1);
}