1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
/******************************************************************************
* Top contributors (to current version):
* Yancheng Ou, Michael Chang
*
* This file is part of the cvc5 project.
*
* Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
* in the top-level source directory and their institutional affiliations.
* All rights reserved. See the file COPYING in the top-level source
* directory for licensing information.
* ****************************************************************************
*
* Optimizer for Integer type.
*/
#include "omt/integer_optimizer.h"
#include "options/smt_options.h"
#include "smt/smt_engine.h"
using namespace cvc5::smt;
namespace cvc5::omt {
OptimizationResult OMTOptimizerInteger::optimize(
SmtEngine* parentSMTSolver,
TNode target,
OptimizationObjective::ObjectiveType objType)
{
// linear search for integer goal
// the smt engine to which we send intermediate queries
// for the linear search.
std::unique_ptr<SmtEngine> optChecker =
OMTOptimizer::createOptCheckerWithTimeout(parentSMTSolver, false);
NodeManager* nm = optChecker->getNodeManager();
Result intermediateSatResult = optChecker->checkSat();
// Model-value of objective (used in optimization loop)
Node value;
if (intermediateSatResult.isUnknown())
{
return OptimizationResult(OptimizationResult::UNKNOWN, value);
}
if (intermediateSatResult.isSat() == Result::UNSAT)
{
return OptimizationResult(OptimizationResult::UNSAT, value);
}
// asserts objective > old_value (used in optimization loop)
Node increment;
Kind incrementalOperator = kind::NULL_EXPR;
if (objType == OptimizationObjective::MINIMIZE)
{
// if objective is MIN, then assert optimization_target <
// current_model_value
incrementalOperator = kind::LT;
}
else if (objType == OptimizationObjective::MAXIMIZE)
{
// if objective is MAX, then assert optimization_target >
// current_model_value
incrementalOperator = kind::GT;
}
// Workhorse of linear search:
// This loop will keep incrmenting/decrementing the objective until unsat
// When unsat is hit,
// the optimized value is the model value just before the unsat call
while (intermediateSatResult.isSat() == Result::SAT)
{
value = optChecker->getValue(target);
Assert(!value.isNull());
increment = nm->mkNode(incrementalOperator, target, value);
optChecker->assertFormula(increment);
intermediateSatResult = optChecker->checkSat();
}
return OptimizationResult(OptimizationResult::OPTIMAL, value);
}
OptimizationResult OMTOptimizerInteger::minimize(
SmtEngine* parentSMTSolver, TNode target)
{
return this->optimize(
parentSMTSolver, target, OptimizationObjective::MINIMIZE);
}
OptimizationResult OMTOptimizerInteger::maximize(
SmtEngine* parentSMTSolver, TNode target)
{
return this->optimize(
parentSMTSolver, target, OptimizationObjective::MAXIMIZE);
}
} // namespace cvc5::omt
|
