mirror of https://github.com/CGAL/cgal
90 lines
3.3 KiB
C++
90 lines
3.3 KiB
C++
// Copyright (c) 2006-2010 Inria Lorraine (France). All rights reserved.
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//
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// This file is part of CGAL (www.cgal.org); you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public License as
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// published by the Free Software Foundation; either version 3 of the License,
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// or (at your option) any later version.
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//
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// Licensees holding a valid commercial license may use this file in
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// accordance with the commercial license agreement provided with the software.
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//
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// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
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// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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//
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// $URL$
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// $Id$
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//
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// Author: Luis Peñaranda <luis.penaranda@gmx.com>
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#ifndef CGAL_RS_SIGN_1_H
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#define CGAL_RS_SIGN_1_H
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#include <gmp.h>
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#include <mpfr.h>
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#include <mpfi.h>
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#include <CGAL/RS/basic.h>
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#include <CGAL/RS/dyadic.h>
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#include <CGAL/RS/polynomial_1.h>
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#include <CGAL/RS/algebraic_1.h>
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#include <CGAL/RS/solve_1.h>
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#include <CGAL/assertions.h>
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namespace CGAL{
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struct RSSign{
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// This function calculates the sign of the evaluation of a polynomial
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// at a given algebraic number. If it is impossible to know the sign
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// evaluating the interval, it calls sign_1_rs, which uses RS to do it.
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static CGAL::Sign sign_1(const RS_polynomial_1 &p,const Algebraic_1 &x){
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RS::rs_sign s=p.sign_mpfi(x.mpfi());
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if(s!=RS::RS_UNKNOWN)
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return RS::convert_rs_sign(s);
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return sign_1_rs(p,x);
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}
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// compute the sign of the polynomial at a given dyadic
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static inline CGAL::Sign
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exactsignatdyadic(const RS_polynomial_1 &p,CGALRS_dyadic_srcptr d){
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return p.sign_dyadic(d);
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}
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// compute the sign of the polynomial at a given mpfr
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static inline CGAL::Sign
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exactsignat(const RS_polynomial_1 &p,mpfr_srcptr m){
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return p.sign_mpfr(m);
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}
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// This function uses interval arithmetic to calculate the sign of the
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// evaluation. First, it converts the given mpfr number to an mpfi
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// interval with the given precision. Later, it evaluates the
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// polynomial in the interval an looks for the sign. If it is not able
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// to determine it, it calls the exact signat function.
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static CGAL::Sign quicksignat
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(const RS_polynomial_1 &p,mpfr_srcptr xcoord,mp_prec_t prec){
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mpfi_t x_approx;
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RS::rs_sign s;
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mpfi_init2(x_approx,prec);
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mpfi_set_fr(x_approx,xcoord);
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s=p.sign_mpfi(x_approx);
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mpfi_clear(x_approx);
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if(s!=RS::RS_UNKNOWN)
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return RS::convert_rs_sign(s);
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return p.sign_mpfr(xcoord);
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}
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// This function is supposed to return the signat calculated in
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// the best way.
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static CGAL::Sign signat(const RS_polynomial_1 &p,mpfr_srcptr xcoord){
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mp_prec_t xprec=mpfr_get_prec(xcoord);
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if(xprec>>(mp_prec_t)12) // switch to exact if xprec>=8192
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return p.sign_mpfr(xcoord);
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return quicksignat(p,xcoord,xprec);
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}
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}; // struct RSSign
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} // namespace CGAL
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#endif // CGAL_RS_SIGN_1_H
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