1 /* ----------------------------------------------------------------------
2     This is the
3 
4     ██╗     ██╗ ██████╗  ██████╗  ██████╗ ██╗  ██╗████████╗███████╗
5     ██║     ██║██╔════╝ ██╔════╝ ██╔════╝ ██║  ██║╚══██╔══╝██╔════╝
6     ██║     ██║██║  ███╗██║  ███╗██║  ███╗███████║   ██║   ███████╗
7     ██║     ██║██║   ██║██║   ██║██║   ██║██╔══██║   ██║   ╚════██║
8     ███████╗██║╚██████╔╝╚██████╔╝╚██████╔╝██║  ██║   ██║   ███████║
9     ╚══════╝╚═╝ ╚═════╝  ╚═════╝  ╚═════╝ ╚═╝  ╚═╝   ╚═╝   ╚══════╝®
10 
11     DEM simulation engine, released by
12     DCS Computing Gmbh, Linz, Austria
13     http://www.dcs-computing.com, office@dcs-computing.com
14 
15     LIGGGHTS® is part of CFDEM®project:
16     http://www.liggghts.com | http://www.cfdem.com
17 
18     Core developer and main author:
19     Christoph Kloss, christoph.kloss@dcs-computing.com
20 
21     LIGGGHTS® is open-source, distributed under the terms of the GNU Public
22     License, version 2 or later. It is distributed in the hope that it will
23     be useful, but WITHOUT ANY WARRANTY; without even the implied warranty
24     of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. You should have
25     received a copy of the GNU General Public License along with LIGGGHTS®.
26     If not, see http://www.gnu.org/licenses . See also top-level README
27     and LICENSE files.
28 
29     LIGGGHTS® and CFDEM® are registered trade marks of DCS Computing GmbH,
30     the producer of the LIGGGHTS® software and the CFDEM®coupling software
31     See http://www.cfdem.com/terms-trademark-policy for details.
32 
33 -------------------------------------------------------------------------
34     Contributing author and copyright for this file:
35     This file is from LAMMPS
36     LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
37     http://lammps.sandia.gov, Sandia National Laboratories
38     Steve Plimpton, sjplimp@sandia.gov
39 
40     Copyright (2003) Sandia Corporation.  Under the terms of Contract
41     DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
42     certain rights in this software.  This software is distributed under
43     the GNU General Public License.
44 ------------------------------------------------------------------------- */
45 
46 #ifndef LMP_MATH_SPECIAL_H
47 #define LMP_MATH_SPECIAL_H
48 
49 #include <cmath>
50 
51 namespace LAMMPS_NS {
52 
53 namespace MathSpecial {
54 
55   // x**2, use instead of pow(x,2.0)
56 
square(const double & x)57   static inline double square(const double &x) { return x*x; }
58 
59   // x**3, use instead of pow(x,3.0)
cube(const double & x)60   static inline double cube(const double &x) { return x*x*x; }
61 
62   // return -1.0 for odd n, 1.0 for even n, like pow(-1.0,n)
powsign(const int n)63   static inline double powsign(const int n) { return (n & 1) ? -1.0 : 1.0; }
64 
65   // optimized version of pow(x,n) with n being integer
66   // up to 10x faster than pow(x,y)
67 
powint(const double & x,const int n)68   static inline double powint(const double &x, const int n) {
69     double yy,ww;
70 
71     if (x == 0.0) return 0.0;
72     int nn = (n > 0) ? n : -n;
73     ww = x;
74 
75     for (yy = 1.0; nn != 0; nn >>= 1, ww *=ww)
76       if (nn & 1) yy *= ww;
77 
78     return (n > 0) ? yy : 1.0/yy;
79   }
80 
81   // optimized version of (sin(x)/x)**n with n being a _positive_ integer
82 
powsinxx(const double & x,int n)83   static inline double powsinxx(const double &x, int n) {
84     double yy,ww;
85 
86     if (x == 0.0) return 1.0;
87 
88     ww = sin(x)/x;
89 
90     for (yy = 1.0; n != 0; n >>= 1, ww *=ww)
91       if (n & 1) yy *= ww;
92 
93     return yy;
94   }
95 }
96 }
97 
98 #endif
99