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#include "dimension.h"
#include "printer.h"
#include "parser.h"
#include "gfanapplication.h"
#include "division.h"
#include "field_rationals.h"
#include "buchberger.h"
class RealRootsApplication : public GFanApplication
{
public:
PolynomialSet sturmPolynomials(Polynomial f1)
{
Polynomial f2=f1.derivative();
PolynomialRing theRing=f1.getRing();
PolynomialSet result(theRing);
result.push_back(f1);
while(!f2.isZero())
{
result.push_back(f2);
PolynomialSet g(theRing);
Polynomial temp=f2;
g.push_back(f2);
g.markAndScale(LexicographicTermOrder());
f2=(f1-f1)-division(f1,g,LexicographicTermOrder());
f1=temp;
}
return result;
}
int numberOfSignChangesAtMinusInfinity(PolynomialSet const &l)
{
int ret=0;
int sign=0;
for(PolynomialSet::const_iterator i=l.begin();i!=l.end();i++)
{
Polynomial p=*i;
p.mark(LexicographicTermOrder());
int newSign=p.getMarked().c.sign()*(1-2*(p.getMarked().m.exponent[0]&1));
if(newSign && (newSign!=sign))
{
ret++;
sign=newSign;
}
}
return ret;
}
int numberOfSignChangesAtInfinity(PolynomialSet const &l)
{
int ret=0;
int sign=0;
for(PolynomialSet::const_iterator i=l.begin();i!=l.end();i++)
{
Polynomial p=*i;
p.mark(LexicographicTermOrder());
int newSign=p.getMarked().c.sign();
if(newSign && (newSign!=sign))
{
ret++;
sign=newSign;
}
}
return ret;
}
int numberOfSignChanges(PolynomialSet const &l, FieldElement const &a)
{
int ret=0;
int sign=0;
for(PolynomialSet::const_iterator i=l.begin();i!=l.end();i++)
{
FieldElement v=i->evaluate(a);
int newSign=v.sign();
if(newSign && (newSign!=sign))
{
ret++;
sign=newSign;
}
}
return ret;
}
/**
* Returns a negative number less than all roots of the polynomial whose Sturm sequence is given.
*/
FieldElement lowerBoundForRoots(PolynomialSet const &l)
{
FieldElement ret=Q.zHomomorphism(-1);
while(numberOfSignChangesAtMinusInfinity(l)!=numberOfSignChanges(l,ret))ret*=Q.zHomomorphism(2);
return ret-Q.zHomomorphism(1);
}
FieldElement upperBoundForRoots(PolynomialSet const &l)
{
FieldElement ret=Q.zHomomorphism(1);
while(numberOfSignChangesAtInfinity(l)!=numberOfSignChanges(l,ret))ret*=Q.zHomomorphism(2);
return ret+Q.zHomomorphism(1);
}
list<FieldElement> intervals(PolynomialSet const &l)
{
list<FieldElement> ret;
FieldElement lo(lowerBoundForRoots(l));
// ret.push_back(a);
while(1)
{
FieldElement hi=upperBoundForRoots(l);
int cLo=numberOfSignChanges(l,lo);
int cHi=numberOfSignChanges(l,hi);
if(cLo<=cHi)break;
{
while(cHi!=cLo-1)
{
FieldElement med=(hi+lo)*Q.zHomomorphism(2).inverse();
int cMed=numberOfSignChanges(l,med);
if(cMed==cLo)
{
lo=med;
cLo=cMed;
}
else
{
hi=med;
cHi=cMed;
}
}
ret.push_back(lo);
ret.push_back(hi);
}
lo=hi;
}
return ret;
}
list<FieldElement> narrow(PolynomialSet const &l, list<FieldElement> intervals, FieldElement epsilon)
{
list<FieldElement> ret;
for(list<FieldElement>::const_iterator i=intervals.begin();i!=intervals.end();i++)
{
FieldElement lo=*i;i++;
FieldElement hi=*i;
while((hi-lo-epsilon).sign()>0)
{
FieldElement med=(hi+lo)*Q.zHomomorphism(2).inverse();
if(numberOfSignChanges(l,med)==numberOfSignChanges(l,hi))
hi=med;
else
lo=med;
}
ret.push_back(lo);
ret.push_back(hi);
}
return ret;
}
//Returns a length that fist in between any two consequtive intervals
FieldElement smallestDistance(list<FieldElement> intervals)
{
FieldElement ret=Q.zHomomorphism(1000);
if(intervals.size()>=4)
{
list<FieldElement>::const_iterator i=intervals.begin();
i++;
for(;i!=intervals.end();i++)
{
FieldElement a=*i;i++;
FieldElement diff=*i-a;
if((diff-ret).sign()<0)ret=diff;
}
}
return ret;
}
/*int numberOfRootsBetweenMinusInfinityAndHere(FieldElement )
{
}*/
bool includeInDefaultInstallation()
{
return false;
}
const char *helpText()
{
return "Not working yet. Given generators for a zero-dimensional ideal this program will compute all real points on the variety.\n";
}
RealRootsApplication() {
registerOptions();
}
const char *name()
{
return "_realroots";
}
int main()
{
FileParser P(Stdin);
PolynomialSet g=P.parsePolynomialSetWithRing();
PolynomialRing r=g.getRing();
int n=r.getNumberOfVariables();
// Polynomial f1=P.parsePolynomialWithRing();
WeightReverseLexicographicTermOrder T(IntegerVector::allOnes(n));
buchberger(&g,T);
debug<<g;
int d=krullDimension(g);
if(0!=d)
{
debug<<"Input ideal is not zero-dimensional.\n";
assert(0);
}
PolynomialRing r2(r.getField(),1);
PolynomialSet projectionPolys(r2);
for(int i=0;i<n;i++)
{
LexicographicTermOrder T((i+1)%n);
buchberger(&g,T);
debug<<g;
list<int> l;
l.push_back(i);
PolynomialSet intersection=g.polynomialRingIntersection(r2,&l);
assert(intersection.size()==1);
projectionPolys.push_back(*intersection.begin());
}
debug<<projectionPolys;
PolynomialSetList sturmPolys;
for(PolynomialSet::const_iterator i=projectionPolys.begin();i!=projectionPolys.end();i++)
{
sturmPolys.push_back(sturmPolynomials(*i));
}
debug.printPolynomialSetList(sturmPolys);
FieldElement bound=Q.zHomomorphism(1);
FieldElement distance=Q.zHomomorphism(1);
for(PolynomialSetList::const_iterator i=sturmPolys.begin();i!=sturmPolys.end();i++)
{
debug<<"Lower "<< lowerBoundForRoots(*i)<<"\n";
debug<<"Upper "<< upperBoundForRoots(*i)<<"\n";
debug<<"Sign changes "<< numberOfSignChangesAtMinusInfinity(*i)<<"\n";
FieldElement s=Q.zHomomorphism(-10000);
debug<<"Sign changes "<< numberOfSignChanges(*i,s)<<"\n";
FieldElement t=Q.zHomomorphism(100000);
debug<<"Sign changes "<< numberOfSignChanges(*i,t)<<"\n";
debug<<"Sign changes "<< numberOfSignChangesAtInfinity(*i)<<"\n";
list<FieldElement> l=intervals(*i);
FieldElement epsilon=(upperBoundForRoots(*i)-lowerBoundForRoots(*i))*Q.zHomomorphism(100).inverse();
l=narrow(*i,l,epsilon);
for(list<FieldElement>::const_iterator j=l.begin();j!=l.end();j++)
debug<<*j<<" "<< fieldElementToFloatingPoint(*j)<<"\n";
FieldElement b=upperBoundForRoots(*i)-lowerBoundForRoots(*i);
// if(bound<b)bound=b;
// FieldElement d=smallestDistance(l);
// if(d<distance)distance=d;
}
/*
FieldElement epsilon2=distance/bound; //<------------------fix this
l=narrow(*i,l,epsilon);
FieldElement delta=epsilon/bound;//<--------------------fix this
PolynomialRing r3=r.withVariablesAppended("W");
Polynomial f=-r3.ithVariable(n);
FieldElement multiplier=Q.zHomomorphism(1);
for(int i=0;i<n;i++)
{
f+=multiplier*r3.ithVariable(i);
multiplier*=delta;
}
PolynomialSet g2=g.embeddedInto(r3);
g2.push_back(f);
*/
/* FieldRationalFunctions k(r.getField(),"t");
PolynomialRing r2(k,n+1);
Polynomial generic(r2)=-r2.ithVariable(n);
for(int i=0;i<n;i++)
generic+=k.exponent(i)*r2.ithVariable(i);
PolynomialSet g2(r2);
g2.push_back(generic);
for(PolynomialSet::const_iterator i=g.begin();i!=g.end();i++)
{
Polynomial f(r2);
for(TermMap::const_iterator j=g.begin();j!=g.end();j++)
{
f+=Term(k.fromCoefficientField(),Monomial(r2,j->first.m.v));
}
g2.push_back(f);
}
pout << g2;
LexicographicTermOrder T2;
buchberger(g2,T2);
Polynomial p(r2);
for(PolynomialSet::const_iterator i=g2.begin();i!=g2.end();i++)
{
if(i->numberOfVariablesInUseConsecutive()==1)p=*i;
}
PolynomialRing r3(k,1);
*/
//AsciiPrinter(Stdout).printPolynomialSet(result);
/* if(evaluateOption.getValue())
{
IntegerVector v=P.parseIntegerVector();
for(int i=0;i<v.size();i++)
{
FieldElement x=Q.zHomomorphism(v[i]);
AsciiPrinter(Stdout).printString("Evaluating in ");
AsciiPrinter(Stdout).printFieldElement(x);
AsciiPrinter(Stdout).printNewLine();
for(PolynomialSet::const_iterator j=result.begin();j!=result.end();j++)
{
AsciiPrinter(Stdout).printFieldElement(j->evaluate(x));
AsciiPrinter(Stdout).printNewLine();
}
}
}
*/
return 0;
}
};
static RealRootsApplication theApplication;
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