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lammps/src/USER-MGPT/mgpt_splinetab.h
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mgpt_splinetab.h
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/* ----------------------------------------------------------------------
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.
See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
This file is part of the MGPT implementation. See further comments
in pair_mgpt.cpp and pair_mgpt.h.
------------------------------------------------------------------------- */
#ifndef SPLINETAB__
#define SPLINETAB__
/*
Given a table of ntab data points tab, assumed to be sampled
on an equidistant grid, compute coefficients of interpolating
cubic polynimials, one per interval (i.e. ntab-1 polynomials).
Input point i is located at tab[i*stride].
Coefficients of output polynomial j are at C[j][0..3];
The piecewise polynimials form a C^2 function which
approximates the input function to fourth order.
The computational cost of this routine is O(ntab).
*/
void makespline(int ntab,int stride,double tab[],double C[][4]);
/*
Evaluate the spline function with coefficients in C (as returned
by makespline()) in point x.
x0 and x1 are the end points of the x points corresponding to
original input interval tab of makespline(). n is ntab-1.
The output is the value (y) of the interpolating spline, and the
first (dy) and second (d2y) dervatives.
The computational cost of this routine is O(1).
*/
void evalspline(int n,double x0,double x1,double C[][4],
double x,double *y,double *dy,double *d2y);
/* Evaluate cubic polynomial represented by p in point x.
The first and second derivatives are also returned.
This can be used to evaluate one of the sub-polynomials
in a spline. */
void evalcubic(double p[4],double x,double *y,double *dy,double *d2y);
#endif
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