/* ----------------------------------------------------------------------
    This is the

    ██╗     ██╗ ██████╗  ██████╗  ██████╗ ██╗  ██╗████████╗███████╗
    ██║     ██║██╔════╝ ██╔════╝ ██╔════╝ ██║  ██║╚══██╔══╝██╔════╝
    ██║     ██║██║  ███╗██║  ███╗██║  ███╗███████║   ██║   ███████╗
    ██║     ██║██║   ██║██║   ██║██║   ██║██╔══██║   ██║   ╚════██║
    ███████╗██║╚██████╔╝╚██████╔╝╚██████╔╝██║  ██║   ██║   ███████║
    ╚══════╝╚═╝ ╚═════╝  ╚═════╝  ╚═════╝ ╚═╝  ╚═╝   ╚═╝   ╚══════╝®

    DEM simulation engine, released by
    DCS Computing Gmbh, Linz, Austria
    http://www.dcs-computing.com, office@dcs-computing.com

    LIGGGHTS® is part of CFDEM®project:
    http://www.liggghts.com | http://www.cfdem.com

    Core developer and main author:
    Christoph Kloss, christoph.kloss@dcs-computing.com

    LIGGGHTS® is open-source, distributed under the terms of the GNU Public
    License, version 2 or later. It 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. You should have
    received a copy of the GNU General Public License along with LIGGGHTS®.
    If not, see http://www.gnu.org/licenses . See also top-level README
    and LICENSE files.

    LIGGGHTS® and CFDEM® are registered trade marks of DCS Computing GmbH,
    the producer of the LIGGGHTS® software and the CFDEM®coupling software
    See http://www.cfdem.com/terms-trademark-policy for details.

-------------------------------------------------------------------------
    Contributing author and copyright for this file:
    This file is from LAMMPS
    LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
    http://lammps.sandia.gov, Sandia National Laboratories
    Steve Plimpton, sjplimp@sandia.gov

    Copyright (2003) Sandia Corporation.  Under the terms of Contract
    DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
    certain rights in this software.  This software is distributed under
    the GNU General Public License.
------------------------------------------------------------------------- */

#ifndef LMP_MATH_SPECIAL_H
#define LMP_MATH_SPECIAL_H

#include <cmath>

namespace LAMMPS_NS {

namespace MathSpecial {

  // x**2, use instead of pow(x,2.0)

  static inline double square(const double &x) { return x*x; }

  // x**3, use instead of pow(x,3.0)
  static inline double cube(const double &x) { return x*x*x; }

  // return -1.0 for odd n, 1.0 for even n, like pow(-1.0,n)
  static inline double powsign(const int n) { return (n & 1) ? -1.0 : 1.0; }

  // optimized version of pow(x,n) with n being integer
  // up to 10x faster than pow(x,y)

  static inline double powint(const double &x, const int n) {
    double yy,ww;

    if (x == 0.0) return 0.0;
    int nn = (n > 0) ? n : -n;
    ww = x;

    for (yy = 1.0; nn != 0; nn >>= 1, ww *=ww)
      if (nn & 1) yy *= ww;

    return (n > 0) ? yy : 1.0/yy;
  }

  // optimized version of (sin(x)/x)**n with n being a _positive_ integer

  static inline double powsinxx(const double &x, int n) {
    double yy,ww;

    if (x == 0.0) return 1.0;

    ww = sin(x)/x;

    for (yy = 1.0; n != 0; n >>= 1, ww *=ww)
      if (n & 1) yy *= ww;

    return yy;
  }
}
}

#endif