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39
40#ifndef QSIMPLEX_P_H
41#define QSIMPLEX_P_H
42
43//
44// W A R N I N G
45// -------------
46//
47// This file is not part of the Qt API. It exists purely as an
48// implementation detail. This header file may change from version to
49// version without notice, or even be removed.
50//
51// We mean it.
52//
53
54#include <QtWidgets/private/qtwidgetsglobal_p.h>
55#include <QtCore/qhash.h>
56#include <QtCore/qpair.h>
57#include <QtCore/qstring.h>
58
59QT_REQUIRE_CONFIG(graphicsview);
60
61QT_BEGIN_NAMESPACE
62
63struct QSimplexVariable
64{
65 QSimplexVariable() : result(0), index(0) {}
66
67 qreal result;
68 int index;
69};
70
71
72/*!
73 \internal
74
75 Representation of a LP constraint like:
76
77 (c1 * X1) + (c2 * X2) + ... = K
78 or <= K
79 or >= K
80
81 Where (ci, Xi) are the pairs in "variables" and K the real "constant".
82*/
83struct QSimplexConstraint
84{
85 QSimplexConstraint() : constant(0), ratio(Equal), artificial(nullptr) {}
86
87 enum Ratio {
88 LessOrEqual = 0,
89 Equal,
90 MoreOrEqual
91 };
92
93 QHash<QSimplexVariable *, qreal> variables;
94 qreal constant;
95 Ratio ratio;
96
97 QPair<QSimplexVariable *, qreal> helper;
98 QSimplexVariable * artificial;
99
100 void invert();
101
102 bool isSatisfied() {
103 qreal leftHandSide(0);
104
105 QHash<QSimplexVariable *, qreal>::const_iterator iter;
106 for (iter = variables.constBegin(); iter != variables.constEnd(); ++iter) {
107 leftHandSide += iter.value() * iter.key()->result;
108 }
109
110 Q_ASSERT(constant > 0 || qFuzzyCompare(1, 1 + constant));
111
112 if ((leftHandSide == constant) || qAbs(t: leftHandSide - constant) < 0.0000001)
113 return true;
114
115 switch (ratio) {
116 case LessOrEqual:
117 return leftHandSide < constant;
118 case MoreOrEqual:
119 return leftHandSide > constant;
120 default:
121 return false;
122 }
123 }
124
125#ifdef QT_DEBUG
126 QString toString() {
127 QString result;
128 result += QString::fromLatin1(str: "-- QSimplexConstraint %1 --").arg(a: quintptr(this), fieldwidth: 0, base: 16);
129
130 QHash<QSimplexVariable *, qreal>::const_iterator iter;
131 for (iter = variables.constBegin(); iter != variables.constEnd(); ++iter) {
132 result += QString::fromLatin1(str: " %1 x %2").arg(a: iter.value()).arg(a: quintptr(iter.key()), fieldwidth: 0, base: 16);
133 }
134
135 switch (ratio) {
136 case LessOrEqual:
137 result += QString::fromLatin1(str: " (less) <= %1").arg(a: constant);
138 break;
139 case MoreOrEqual:
140 result += QString::fromLatin1(str: " (more) >= %1").arg(a: constant);
141 break;
142 default:
143 result += QString::fromLatin1(str: " (eqal) == %1").arg(a: constant);
144 }
145
146 return result;
147 }
148#endif
149};
150
151class QSimplex
152{
153 Q_DISABLE_COPY_MOVE(QSimplex)
154public:
155 QSimplex();
156 ~QSimplex();
157
158 qreal solveMin();
159 qreal solveMax();
160
161 bool setConstraints(const QList<QSimplexConstraint *> &constraints);
162 void setObjective(QSimplexConstraint *objective);
163
164 void dumpMatrix();
165
166private:
167 // Matrix handling
168 inline qreal valueAt(int row, int column);
169 inline void setValueAt(int row, int column, qreal value);
170 void clearRow(int rowIndex);
171 void clearColumns(int first, int last);
172 void combineRows(int toIndex, int fromIndex, qreal factor);
173
174 // Simplex
175 bool simplifyConstraints(QList<QSimplexConstraint *> *constraints);
176 int findPivotColumn();
177 int pivotRowForColumn(int column);
178 void reducedRowEchelon();
179 bool iterate();
180
181 // Helpers
182 void clearDataStructures();
183 void solveMaxHelper();
184 enum SolverFactor { Minimum = -1, Maximum = 1 };
185 qreal solver(SolverFactor factor);
186 void collectResults();
187
188 QList<QSimplexConstraint *> constraints;
189 QList<QSimplexVariable *> variables;
190 QSimplexConstraint *objective;
191
192 int rows;
193 int columns;
194 int firstArtificial;
195
196 qreal *matrix;
197};
198
199inline qreal QSimplex::valueAt(int rowIndex, int columnIndex)
200{
201 return matrix[rowIndex * columns + columnIndex];
202}
203
204inline void QSimplex::setValueAt(int rowIndex, int columnIndex, qreal value)
205{
206 matrix[rowIndex * columns + columnIndex] = value;
207}
208
209QT_END_NAMESPACE
210
211#endif // QSIMPLEX_P_H
212

source code of qtbase/src/widgets/graphicsview/qsimplex_p.h