/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | Copyright (C) 2016 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.

    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.

    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.

\*---------------------------------------------------------------------------*/

#include "AMC.H"

#include "error.H"

// * * * * * * * * * * * * * Functions * * * * * * * * * * * * //

//Amplitude Mapping Closure (from KIVA)
//Define exp(-2*(erf^-1(2*eta - 1))^2)
inline Foam::scalar Foam::CMC::AMC(const scalar eta)
{
    const scalar a0 = (2.0*eta - 1.0);
    scalar a1 = 0.5;
    scalar slope;
    scalar da = GREAT;

    while(mag(da) > SMALL)
    {
        slope = (2.0/spi)*Foam::exp(-1.0*Foam::pow(a1,2.0));
        da = (a0 - Foam::erf(a1))/slope;
        a1 = a1 + da;
    }

    return Foam::exp(-2.0*Foam::pow(a1,2.0));
}

//Amplitude Mapping Closure (from KIVA)
Foam::tmp<Foam::scalarField> Foam::CMC::AMC(const scalarField& eta)
{
    tmp<scalarField> tRes(new scalarField(eta.size(), 0.0));

    scalarField& Res = tRes.ref();

    for(label i=0 ; i<eta.size() ; i++)
    {
        Res[i] = AMC(eta[i]);
    }

    return tRes;
}



// ************************************************************************* //