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/*
This file is part of PolyLib.
PolyLib 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.
PolyLib 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 PolyLib. If not, see <http://www.gnu.org/licenses/>.
*/
/** homogenization.c
copyright 2004-2005 Bavo Nootaert
**/
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <polylib/polylib.h>
#include <polylib/homogenization.h>
static evalue *dehomogenize_periodic(enode *en);
static evalue *dehomogenize_polynomial(enode *en);
Polyhedron *homogenize(Polyhedron *P, unsigned MAXRAYS)
{
Matrix M, *M2;
/* Pretend P is a Matrix for a second */
M.NbRows = P->NbConstraints;
M.NbColumns = P->Dimension+2;
M.p_Init = P->p_Init;
M.p = P->Constraint;
M2 = AddANullColumn(&M);
P = Constraints2Polyhedron(M2, MAXRAYS);
Matrix_Free(M2);
return P;
}
/** dehomogenize an evalue. The last parameter (nb_param) is replaced by 1.
This function is mutually recursive with dehomogenize_enode.
**/
void dehomogenize_evalue(evalue *ep, int nb_param){
evalue *w;
/** cannot dehomogenize rationals **/
if (value_zero_p(ep->d)){
/** we need to replace the last parameter **/
if (ep->x.p->pos == nb_param){
if (ep->x.p->type == periodic && ep->x.p->size > 1){
w = dehomogenize_periodic(ep->x.p);
}
else{
w = dehomogenize_polynomial(ep->x.p);
}
free_evalue_refs(ep);
memcpy(ep, w, sizeof(evalue));
free(w);
}
else{
/** Not the last parameter. Recurse **/
dehomogenize_enode(ep->x.p, nb_param);
}
}
}
/** dehomogenize all evalues in an enode.
This function is mutually recursive with dehomogenize_evalue.
**/
void dehomogenize_enode(enode *p, int nb_param){
evalue *temp;
int i;
for (i = 0; i < p->size; i++){
dehomogenize_evalue(&p->arr[i], nb_param);
}
}
/** return the 1st element of an enode representing a periodic **/
static evalue *dehomogenize_periodic(enode *en){
evalue *w;
assert(en->type == periodic);
assert(en->size > 1);
assert(value_notzero_p(en->arr[1].d));
w = (evalue*)malloc(sizeof(evalue));
value_init(w->d); value_init(w->x.n);
value_assign(w->d, en->arr[1].d); value_assign(w->x.n, en->arr[1].x.n);
return w;
}
/** dehomogenize a polynomial. Assume the enode contains a polynomial in
one variable, the homogenous parameter.
Returns an new evalue, representing a rational.
**/
static evalue *dehomogenize_polynomial(enode *en){
evalue *enn;
evalue *ev;
int i;
double som;
Value num, den, gcd, f1, f2;
assert(en->type == polynomial);
som = 0;
value_init(num); value_init(den); value_init(gcd);
value_init(f1); value_init(f2);
value_set_si(den, 1);
/** enumerate over all coefficients (which are either periodic or rational,
but not polynomial) **/
for (i = 0; i < en->size; i++){
if (value_zero_p(en->arr[i].d)){
if (en->arr[i].x.p->size > 1)
ev = &en->arr[i].x.p->arr[1];
else
ev = &en->arr[i].x.p->arr[0];
}
else{
ev = &en->arr[i];
}
/** add ev (fraction) to num/den **/
value_multiply(f1, den, ev->x.n);
value_multiply(f2, num, ev->d);
value_addto(num, f1, f2);
value_multiply(den, den, ev->d);
}
/** simplify num/den **/
value_gcd(gcd, num, den);
value_divexact(num, num, gcd);
value_divexact(den, den, gcd);
/** create new evalue representing num/den**/
enn = (evalue*)malloc(sizeof(evalue));
value_init(enn->d); value_init(enn->x.n);
value_assign(enn->d, den);
value_assign(enn->x.n, num);
/** cleanup **/
value_clear(gcd);
value_clear(f1); value_clear(f2);
value_clear(num); value_clear(den);
return enn;
}
/** dehomogenize a polyhedron. Assume the polyhedron p is homogenous.
Returns a new polyhedron.
**/
Polyhedron *dehomogenize_polyhedron(Polyhedron *p, int maxRays){
Matrix *constr, *constrh;
Polyhedron *ph;
int i;
constr = Polyhedron2Constraints(p);
constrh = Matrix_Alloc(constr->NbRows, constr->NbColumns - 1);
for (i = 0; i < constr->NbRows; i++){
Vector_Copy(constr->p[i], constrh->p[i], constr->NbColumns - 1);
}
ph = Constraints2Polyhedron(constrh, maxRays);
Matrix_Free(constr); Matrix_Free(constrh);
return ph;
}
/** dehomogenize an enumeration. Replaces each validity domain and
Ehrhart polynomial in the Enumeration en with the dehomogenized form.
**/
void dehomogenize_enumeration(Enumeration* en, int nb_params, int maxRays){
Enumeration *en2;
Polyhedron *vd;
for (en2 = en; en2; en2 = en2->next) {
vd = dehomogenize_polyhedron(en2->ValidityDomain, maxRays);
Polyhedron_Free(en2->ValidityDomain);
en2->ValidityDomain = vd;
dehomogenize_evalue(&en2->EP, nb_params);
}
}
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