LA_library/polynomial.h

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/*
LA: linear algebra C++ interface library
Copyright (C) 2021 Jiri Pittner <jiri.pittner@jh-inst.cas.cz> or <jiri@pittnerovi.com>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _POLYNOMIAL_H
#define _POLYNOMIAL_H
#include "la_traits.h"
#include "vec.h"
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#include "nonclass.h"
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namespace LA {
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template <typename T>
class Polynomial : public NRVec<T> {
public:
Polynomial(): NRVec<T>() {};
Polynomial(const NRVec<T> &v) : NRVec<T>(v) {}; //allow implicit conversion from NRVec
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Polynomial(const int n) : NRVec<T>(n+1) {};
Polynomial(const T &a, const int n) : NRVec<T>(n+1) {NRVec<T>::clear(); (*this)[0]=a;};
int degree() const {return NRVec<T>::size()-1;};
void resize(const int n, const bool preserve=true) {NRVec<T>::resize(n+1,preserve);}
Polynomial& operator+=(const T &a) {NOT_GPU(*this); NRVec<T>::copyonwrite(); (*this)[0]+=a; return *this;}
Polynomial& operator-=(const T &a) {NOT_GPU(*this); NRVec<T>::copyonwrite(); (*this)[0]-=a; return *this;}
Polynomial operator+(const T &a) const {return Polynomial(*this) += a;};
Polynomial operator-(const T &a) const {return Polynomial(*this) -= a;};
Polynomial operator-() const {return NRVec<T>::operator-();}
Polynomial operator*(const T &a) const {return NRVec<T>::operator*(a);}
Polynomial operator/(const T &a) const {return NRVec<T>::operator/(a);}
Polynomial& operator*=(const T &a) {NRVec<T>::operator*=(a); return *this;}
Polynomial& operator/=(const T &a) {NRVec<T>::operator/=(a); return *this;}
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Polynomial& operator+=(const Polynomial &rhs)
{
NOT_GPU(*this); NRVec<T>::copyonwrite();
if(rhs.degree()>degree()) resize(rhs.degree(),true);
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for(int i=0; i<=rhs.degree(); ++i) (*this)[i] += rhs[i];
return *this;
}
Polynomial& operator-=(const Polynomial &rhs)
{
NOT_GPU(*this); NRVec<T>::copyonwrite();
if(rhs.degree()>degree()) resize(rhs.degree(),true);
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for(int i=0; i<=rhs.degree(); ++i) (*this)[i] -= rhs[i];
return *this;
}
Polynomial operator+(const Polynomial &rhs) const {return Polynomial(*this) += rhs;};
Polynomial operator-(const Polynomial &rhs) const {return Polynomial(*this) -= rhs;};
Polynomial operator*(const Polynomial &rhs) const //for very long polynomials FFT should be used
{
NOT_GPU(*this);
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Polynomial r(degree()+rhs.degree());
r.clear();
for(int i=0; i<=rhs.degree(); ++i) for(int j=0; j<=degree(); ++j) r[i+j] += rhs[i]*(*this)[j];
return r;
};
Polynomial& operator*=(const Polynomial &rhs) {*this = (*this)*rhs; return *this;};
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void simplify(const typename LA_traits<T>::normtype thr=0)
{
NOT_GPU(*this);
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this->copyonwrite();
int n=degree();
while(n>0 && MYABS((*this)[n])<=thr) --n;
resize(n,true);
};
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void normalize() {if((*this)[degree()]==(T)0) laerror("zero coefficient at highest degree - simplify first"); *this /= (*this)[degree()];};
Polynomial shifted(const int shift) const
{
if(shift==0) return *this;
if(shift>0)
{
Polynomial r(degree()+shift);
for(int i=0; i<shift; ++i) r[i]=0;
for(int i=0; i<=degree(); ++i) r[shift+i] = (*this)[i];
return r;
}
else
{
if(shift+degree()<0)
{
Polynomial r(0);
r[0]=0;
return r;
}
Polynomial r(shift+degree());
for(int i= -shift; i<=degree(); ++i) r[shift+i] = (*this)[i];
return r;
}
}
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Polynomial derivative(const int d=1) const
{
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if(d==0) return *this;
if(d<0) return integral(-d);
NOT_GPU(*this);
int n=degree();
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if(n-d<0)
{
Polynomial r(0);
r[0]=0;
return r;
}
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Polynomial r(n-d);
for(int i=d; i<=n; ++i)
{
int prod=1;
for(int j=i; j>=i-d+1; --j) prod *= j;
r[i-d] = (*this)[i]* ((T)prod);
}
return r;
};
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Polynomial integral(const int d=1) const
{
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if(d==0) return *this;
if(d<0) return derivative(-d);
NOT_GPU(*this);
int n=degree();
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Polynomial r(n+d);
for(int i=0; i<d; ++i) r[i]=0;
for(int i=0; i<=n; ++i)
{
int prod=1;
for(int j=i+1; j<=i+d;++j) prod *= j;
r[i+d] = (*this)[i]/((T)prod);
}
return r;
}
void polydiv(const Polynomial &rhs, Polynomial &q, Polynomial &r) const;
Polynomial operator/(const Polynomial &rhs) const {Polynomial q,r; polydiv(rhs,q,r); return q;};
Polynomial operator%(const Polynomial &rhs) const {Polynomial q,r; polydiv(rhs,q,r); return r;};
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NRMat<T> companion() const; //matrix which has this characteristic polynomial
NRVec<typename LA_traits<T>::complextype> roots() const; //implemented for complex<double> and double only
NRVec<T> realroots(const typename LA_traits<T>::normtype thr) const;
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T newton(const T x0, const typename LA_traits<T>::normtype thr=1e-14, const int maxit=1000) const; //solve root from the guess
Polynomial pow(const int i) const; //integer power
Polynomial powx(const int i) const; //substitute x^i for x in the polynomial
void binomial(const int n); //(1+x)^n
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};
//this is very general, can be used also for composition (nesting) of polynomials
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//for an alternative algorithm which minimizes number of multiplications cf. also matexp.h
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template <typename T, typename C>
C value(const Polynomial<T> &p, const C &x)
{
C sum(x);
sum=0; //get matrix dimension if C is a matrix
for(int i=p.degree(); i>0; --i)
{
sum+= p[i];
sum= sum*x; //not *= for matrices
}
sum += p[0];
return sum;
}
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template <typename T, typename C>
NRVec<C> values(const Polynomial<T> &p, const NRVec<C> &x)
{
NRVec<C> r(x.size());
for(int i=0; i<x.size(); ++i) r[i]=value(p,x[i]);
return r;
}
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//scalar+-polynomial
template <typename T>
inline Polynomial<T> operator+(const T &a, const Polynomial<T> &rhs) {return Polynomial<T>(rhs)+=a;}
template <typename T>
inline Polynomial<T> operator-(const T &a, const Polynomial<T> &rhs) {return Polynomial<T>(rhs)-=a;}
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//Sylvester matrix
template <typename T>
extern NRMat<T> Sylvester(const Polynomial<T> &p, const Polynomial<T> &q);
//polynomial from given roots
template <typename T>
Polynomial<T> polyfromroots(const NRVec<T> &roots, const int skip= -1)
{
Polynomial<T> p(0);
p[0]=(T)1;
for(int i=0; i<roots.size(); ++i)
if(i!=skip)
p = p.shifted(1) - p * roots[i];
return p;
}
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template <typename T>
extern Polynomial<T> lagrange_interpolation(const NRVec<T> &x, const NRVec<T> &y);
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template <typename T>
extern Polynomial<T> poly_gcd(const Polynomial<T> &p, const Polynomial<T> &q, const typename LA_traits<T>::normtype thr=0, const int d= -1);
template <typename T>
extern Polynomial<T> svd_gcd(const Polynomial<T> &p, const Polynomial<T> &q, const typename LA_traits<T>::normtype thr=0);
template <typename T>
Polynomial<T> poly_lcm(const Polynomial<T> &p, const Polynomial<T> &q, const typename LA_traits<T>::normtype thr=0)
{
return p*q/poly_gcd(p,q,thr);
}
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}//namespace
#endif