Frobby 0.9.5
Deformer.cpp
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1/* Frobby: Software for monomial ideal computations.
2 Copyright (C) 2010 University of Aarhus
3 Contact Bjarke Hammersholt Roune for license information (www.broune.com)
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2 of the License, or
8 (at your option) any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see http://www.gnu.org/licenses/.
17*/
18#include "stdinc.h"
19#include "Deformer.h"
20
21#include "Term.h"
22#include "TermPredicate.h"
23#include "Ideal.h"
24#include "TermPredicate.h"
25#include "error.h"
26#include "IdealOrderer.h"
27#include <map>
28
29namespace {
30 void deform(Ideal& ideal,
31 vector<Exponent>& undeform,
32 size_t var,
33 bool stronglyGeneric) {
34 ASSERT(undeform.empty());
35
36 map<Exponent, vector<Exponent*> > exps;
37
38 Ideal::const_iterator end = ideal.end();
39 for (Ideal::const_iterator it = ideal.begin(); it != end; ++it) {
40 Exponent& e = (*it)[var];
41 if (e == 0)
42 continue;
43 exps[e].push_back(*it);
44 }
45
46 Term tmp(ideal.getVarCount());
47 undeform.push_back(0); // zero always maps to zero
48 for (map<Exponent, vector<Exponent*> >::iterator it = exps.begin();
49 it != exps.end(); ++it) {
50 vector<Exponent*>& block = it->second;
51
52 typedef vector<Exponent*>::iterator BlockIt;
53 if (stronglyGeneric) {
54 for (BlockIt blockIt = block.begin(); blockIt != block.end();
55 ++blockIt) {
56 undeform.push_back((*blockIt)[var]);
57 (*blockIt)[var] = undeform.size() - 1;
58 }
59 } else {
60 undeform.push_back(block.front()[var]);
61 Exponent sharedDeformedExponent = undeform.size() - 1;
62
63 for (BlockIt blockIt = block.begin(); blockIt != block.end();
64 ++blockIt) {
65 bool canUseShared = true;
66 for (BlockIt other = blockIt + 1; other != block.end(); ++other) {
67 tmp.lcm(*blockIt, *other);
68 if (!ideal.strictlyContains(tmp)) {
69 canUseShared = false;
70 break;
71 }
72 }
73 if (canUseShared)
74 (*blockIt)[var] = sharedDeformedExponent;
75 else {
76 undeform.push_back((*blockIt)[var]);
77 (*blockIt)[var] = undeform.size() - 1;
78 }
79 }
80 }
81 }
82 }
83}
84
86 const IdealOrderer& orderer,
87 bool stronglyGeneric):
88 _undeform(ideal.getVarCount()) {
89
90 orderer.order(ideal);
91
92 for (size_t var = 0; var < ideal.getVarCount(); ++var)
93 deform(ideal, _undeform[var], var, stronglyGeneric);
94
95 ASSERT(!stronglyGeneric || ideal.isStronglyGeneric());
96 ASSERT(ideal.isWeaklyGeneric());
97}
98
99void Deformer::undeform(Term& term) const {
100 ASSERT(term.getVarCount() == _undeform.size());
101
102 for (size_t var = 0; var < term.getVarCount(); ++var) {
103 ASSERT(term[var] < _undeform[var].size());
104 term[var] = _undeform[var][term[var]];
105 }
106}
Deformer(Ideal &ideal, const IdealOrderer &deformationOrder, bool makeStronglyGeneric=true)
Apply a generic deformation to ideal such that it becomes generic.
Definition Deformer.cpp:85
vector< vector< Exponent > > _undeform
var^e undeforms to var^(_undeform[var][e]).
Definition Deformer.h:53
void undeform(Term &term) const
Apply the reverse transformation on term than that applied to the Ideal passed to the constructor.
Definition Deformer.cpp:99
void order(Ideal &ideal) const
Represents a monomial ideal with int exponents.
Definition Ideal.h:27
bool strictlyContains(const Exponent *term) const
Definition Ideal.cpp:73
const_iterator end() const
Definition Ideal.h:49
const_iterator begin() const
Definition Ideal.h:48
bool isWeaklyGeneric() const
Definition Ideal.cpp:121
bool isStronglyGeneric()
Definition Ideal.cpp:106
Cont::const_iterator const_iterator
Definition Ideal.h:43
size_t getVarCount() const
Definition Ideal.h:56
Term represents a product of variables which does not include a coefficient.
Definition Term.h:49
size_t getVarCount() const
Definition Term.h:85
This header file includes common definitions and is included as the first line of code in every imple...
unsigned int Exponent
Definition stdinc.h:89
#define ASSERT(X)
Definition stdinc.h:86