math/switch.h

#pragma once
#include "ff/precision.h"
#include "seq/seq.h"
 
namespace tinker {
#pragma acc routine seq
template <int DO_DTAPER>
SEQ_CUDA
void switchTaper5(real rik, real cut, real off, real& restrict taper,
   real& restrict dtaper)
{
   real rinv = 1 / (cut - off);
   real x = (rik - off) * rinv;
   real x2 = x * x;
   real x3 = x2 * x;
   taper = x3 * (6 * x2 - 15 * x + 10);
   if CONSTEXPR (DO_DTAPER) dtaper = 30 * (x * (1 - x)) * (x * (1 - x)) * rinv;
}
}