source: ThirdParty/mpqc_open/src/lib/math/scmat/offset.h@ 37fe17

//
// offset.h
//
// Copyright (C) 1996 Limit Point Systems, Inc.
//
// Author: Curtis Janssen <cljanss@ca.sandia.gov>
// Maintainer: LPS
//
// This file is part of the SC Toolkit.
//
// The SC Toolkit is free software; you can redistribute it and/or modify
// it under the terms of the GNU Library General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// The SC Toolkit 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 Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public License
// along with the SC Toolkit; see the file COPYING.LIB.  If not, write to
// the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
//
// The U.S. Government is granted a limited license as per AL 91-7.
//

#ifndef _math_scmat_offset_h
#define _math_scmat_offset_h

#ifdef __c_plus_plus

namespace sc {

static inline int
i_offset(int i)
{
  return ((i*(i+1)) >> 1);
}

static inline int
ij_offset(int i, int j)
{
  return (i>j) ? (((i*(i+1)) >> 1) + j) : (((j*(j+1)) >> 1) + i);
}

static inline int
igtj_offset(int i, int j)
{
  return ((i*(i+1)) >> 1) + j;
}

}

#else

#define i_offset(i) (((i)*((i)+1))>>1)
#define ij_offset(i,j) (((i)>(j))?(i_offset(i)+(j)):(i_offset(j)+(i)))
#define igtj_offset(i,j) (i_offset(i)+(j))

#endif

#endif