/* ----------------------------------------------------------------------
   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator 

   Original Version:
   http://lammps.sandia.gov, Sandia National Laboratories
   Steve Plimpton, sjplimp@sandia.gov 

   See the README file in the top-level LAMMPS directory. 

   ----------------------------------------------------------------------- 

   USER-CUDA Package and associated modifications:
   https://sourceforge.net/projects/lammpscuda/ 

   Christian Trott, christian.trott@tu-ilmenau.de
   Lars Winterfeld, lars.winterfeld@tu-ilmenau.de
   Theoretical Physics II, University of Technology Ilmenau, Germany 

   See the README file in the USER-CUDA directory. 

   This software is distributed under the GNU General Public License.
------------------------------------------------------------------------- */

__device__ inline F_FLOAT PairLJGromacsCuda_Eval(const F_FLOAT& rsq,const int ij_type,F_FLOAT& factor_lj,int& eflag, ENERGY_FLOAT& evdwl)
{
	F_FLOAT tlj;
	const F_FLOAT r2inv = F_F(1.0)/rsq;
	const F_FLOAT r = _RSQRT_(r2inv);
	const F_FLOAT r6inv = r2inv*r2inv*r2inv;
	F_FLOAT	forcelj = r6inv * (_lj1[ij_type]*r6inv - _lj2[ij_type]);
	const X_FLOAT cut_lj_innersq=(_cut_innersq_global > X_F(0.0)? _cut_innersq_global : _cut_innersq[ij_type]);
	if (rsq > cut_lj_innersq)
	{
		tlj = r - _SQRT_(cut_lj_innersq);
	    forcelj += r*tlj*tlj*(_ljsw1[ij_type] + _ljsw2[ij_type]*tlj);
	}
				
    if (eflag) 
    {
    	ENERGY_FLOAT evdwl_tmp = r6inv*(_lj3[ij_type]*r6inv-_lj4[ij_type]);
	      									 		
    	if (rsq > cut_lj_innersq) 
    	{
			  evdwl_tmp += tlj*tlj*tlj*
			  	(_ljsw3[ij_type] + _ljsw4[ij_type]*tlj) + _ljsw5[ij_type];;
    	}
			    	
    	evdwl+=evdwl_tmp*factor_lj;
    }
    return factor_lj*forcelj*r2inv;
}
