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support for domain splitting value strategy

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This commit is contained in:
lperron@google.com
2012-06-10 09:51:16 +00:00
parent f7a84fc77c
commit ed927ca9ea
2 changed files with 71 additions and 18 deletions
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12
src/constraint_solver/constraint_solver.h
View File

@@ -452,8 +452,8 @@ class Solver {
CHOOSE_PATH,
};
// This enum describes the strategy used to select the next variable value to
// set.
// This enum describes the strategy used to select the next decision
// to apply on this variable.
enum IntValueStrategy {
// The default behavior is ASSIGN_MIN_VALUE.
INT_VALUE_DEFAULT,
@@ -474,6 +474,14 @@ class Solver {
// of the domain of the selected variable.
// The center is defined as (min + max) / 2.
ASSIGN_CENTER_VALUE,
// Split the domain in two around the center, and choose the lower
// part first.
SPLIT_LOWER_HALF,
// Split the domain in two around the center, and choose the lower
// part first.
SPLIT_UPPER_HALF,
};
// This enum is used by Solver::MakePhase to specify how to select variables

77
src/constraint_solver/search.cc
View File

@@ -1215,10 +1215,15 @@ int64 RandomValueSelector::Select(const IntVar* const v, int64 id) {
class CenterValueSelector : public ValueSelector {
public:
CenterValueSelector() {}
CenterValueSelector(const string& name) : name_(name) {}
virtual ~CenterValueSelector() {}
virtual int64 Select(const IntVar* const v, int64 id);
string DebugString() const { return "AssignCenter"; }
string DebugString() const {
return name_;
}
private:
const string name_;
};
int64 CenterValueSelector::Select(const IntVar* const v, int64 id) {
@@ -1756,8 +1761,15 @@ Decision* Solver::MakeAssignVariablesValues(const std::vector<IntVar*>& vars,
namespace {
class BaseAssignVariables : public DecisionBuilder {
public:
explicit BaseAssignVariables(BaseVariableAssignmentSelector* const selector)
: selector_(selector) {}
enum Mode {
ASSIGN,
SPLIT_LOWER,
SPLIT_UPPER,
};
explicit BaseAssignVariables(BaseVariableAssignmentSelector* const selector,
Mode mode)
: selector_(selector), mode_(mode) {}
virtual ~BaseAssignVariables();
virtual Decision* Next(Solver* const s);
virtual string DebugString() const;
@@ -1765,7 +1777,8 @@ class BaseAssignVariables : public DecisionBuilder {
const IntVar* const* vars,
int size,
VariableSelector* const var_selector,
ValueSelector* const value_selector);
ValueSelector* const value_selector,
BaseAssignVariables::Mode mode);
static VariableSelector* MakeVariableSelector(Solver* const s,
const IntVar* const* vars,
int size,
@@ -1830,7 +1843,13 @@ class BaseAssignVariables : public DecisionBuilder {
value_selector = s->RevAlloc(new RandomValueSelector);
break;
case Solver::ASSIGN_CENTER_VALUE:
value_selector = s->RevAlloc(new CenterValueSelector);
value_selector = s->RevAlloc(new CenterValueSelector("AssignCenter"));
break;
case Solver::SPLIT_LOWER_HALF:
value_selector = s->RevAlloc(new CenterValueSelector("SplitLower"));
break;
case Solver::SPLIT_UPPER_HALF:
value_selector = s->RevAlloc(new CenterValueSelector("SplitUpper"));
break;
default:
LOG(FATAL) << "Unknown int value strategy " << val_str;
@@ -1845,6 +1864,7 @@ class BaseAssignVariables : public DecisionBuilder {
protected:
BaseVariableAssignmentSelector* const selector_;
const Mode mode_;
};
BaseAssignVariables::~BaseAssignVariables() {}
@@ -1854,7 +1874,14 @@ Decision* BaseAssignVariables::Next(Solver* const s) {
IntVar* const var = selector_->SelectVariable(s, &id);
if (NULL != var) {
const int64 value = selector_->SelectValue(var, id);
return s->RevAlloc(new AssignOneVariableValue(var, value));
switch (mode_) {
case ASSIGN:
return s->RevAlloc(new AssignOneVariableValue(var, value));
case SPLIT_LOWER:
return s->RevAlloc(new SplitOneVariable(var, value, true));
case SPLIT_UPPER:
return s->RevAlloc(new SplitOneVariable(var, value, false));
}
}
return NULL;
}
@@ -1868,10 +1895,11 @@ BaseAssignVariables::MakePhase(Solver* const s,
const IntVar* const* vars,
int size,
VariableSelector* const var_selector,
ValueSelector* const value_selector) {
ValueSelector* const value_selector,
BaseAssignVariables::Mode mode) {
BaseVariableAssignmentSelector* selector =
s->RevAlloc(new VariableAssignmentSelector(var_selector, value_selector));
return s->RevAlloc(new BaseAssignVariables(selector));
return s->RevAlloc(new BaseAssignVariables(selector, mode));
}
} // namespace
@@ -1919,6 +1947,16 @@ DecisionBuilder* Solver::MakePhase(IntVar* const v0,
return MakePhase(vars, var_str, val_str);
}
BaseAssignVariables::Mode ChooseMode(Solver::IntValueStrategy val_str) {
BaseAssignVariables::Mode mode = BaseAssignVariables::ASSIGN;
if (val_str == Solver::SPLIT_LOWER_HALF) {
mode = BaseAssignVariables::SPLIT_LOWER;
} else if (val_str == Solver::SPLIT_UPPER_HALF) {
mode = BaseAssignVariables::SPLIT_UPPER;
}
return mode;
}
DecisionBuilder* Solver::MakePhase(const std::vector<IntVar*>& vars,
Solver::IntVarStrategy var_str,
Solver::IntValueStrategy val_str) {
@@ -1933,7 +1971,8 @@ DecisionBuilder* Solver::MakePhase(const std::vector<IntVar*>& vars,
vars.data(),
vars.size(),
var_selector,
value_selector);
value_selector,
ChooseMode(val_str));
}
DecisionBuilder* Solver::MakePhase(const std::vector<IntVar*>& vars,
@@ -1950,7 +1989,8 @@ DecisionBuilder* Solver::MakePhase(const std::vector<IntVar*>& vars,
vars.data(),
vars.size(),
var_selector,
value_selector);
value_selector,
ChooseMode(val_str));
}
DecisionBuilder* Solver::MakePhase(
@@ -1969,7 +2009,8 @@ DecisionBuilder* Solver::MakePhase(
vars.data(),
vars.size(),
var_selector,
value_selector);
value_selector,
BaseAssignVariables::ASSIGN);
}
DecisionBuilder* Solver::MakePhase(
@@ -1988,7 +2029,8 @@ DecisionBuilder* Solver::MakePhase(
vars.data(),
vars.size(),
var_selector,
value_selector);
value_selector,
BaseAssignVariables::ASSIGN);
}
DecisionBuilder* Solver::MakePhase(
@@ -2008,7 +2050,8 @@ DecisionBuilder* Solver::MakePhase(
vars.data(),
vars.size(),
var_selector,
value_selector);
value_selector,
BaseAssignVariables::ASSIGN);
}
DecisionBuilder* Solver::MakePhase(
@@ -2028,7 +2071,8 @@ DecisionBuilder* Solver::MakePhase(
vars.data(),
vars.size(),
var_selector,
value_selector);
value_selector,
BaseAssignVariables::ASSIGN);
}
DecisionBuilder* Solver::MakePhase(const std::vector<IntVar*>& vars,
@@ -2062,7 +2106,8 @@ DecisionBuilder* Solver::MakePhase(const std::vector<IntVar*>& vars,
break;
}
}
return RevAlloc(new BaseAssignVariables(selector));
return RevAlloc(new BaseAssignVariables(selector,
BaseAssignVariables::ASSIGN));
}
// ----- AssignAllVariablesFromAssignment decision builder -----