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Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
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Leonardo de Moura 2012-10-02 11:35:25 -07:00
parent 3f9edad676
commit e9eab22e5c
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107
lib/spc_literal_selection.cpp Normal file
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/*++
Copyright (c) 2006 Microsoft Corporation
Module Name:
spc_literal_selection.cpp
Abstract:
Superposition Calculus Literal Selection
Author:
Leonardo de Moura (leonardo) 2008-02-05.
Revision History:
--*/
#include"spc_literal_selection.h"
#include"expr_stat.h"
namespace spc {
void diff_literal_selection::operator()(clause * cls) {
bool found = false;
unsigned target = UINT_MAX;
unsigned best_count = 0;
unsigned num = cls->get_num_literals();
for (unsigned i = 0; i < num; i++) {
literal & l = cls->get_literal(i);
if (l.sign()) {
unsigned count;
if (m_manager.is_eq(l.atom())) {
unsigned c1 = get_symbol_count(to_app(l.atom())->get_arg(0));
unsigned c2 = get_symbol_count(to_app(l.atom())->get_arg(1));
count = c1 >= c2 ? c1 - c2 : c2 - c1;
}
else {
count = get_symbol_count(l.atom());
}
if (count > best_count) {
found = true;
target = i;
best_count = count;
}
}
}
if (found)
cls->select_literal(target);
}
void complex_literal_selection::operator()(clause * cls) {
// look for x != y
unsigned num = cls->get_num_literals();
for (unsigned i = 0; i < num; i++) {
literal & l = cls->get_literal(i);
if (l.sign() && m_manager.is_eq(l.atom()) && is_var(to_app(l.atom())->get_arg(0)) && is_var(to_app(l.atom())->get_arg(1))) {
cls->select_literal(i);
return;
}
}
// look for min ground neg literal
bool found = false;
unsigned target = UINT_MAX;
unsigned best_count = UINT_MAX;
for (unsigned i = 0; i < num; i++) {
literal & l = cls->get_literal(i);
if (l.sign() && is_ground(l.atom())) {
unsigned count = get_symbol_count(l.atom());
if (count < best_count) {
found = true;
target = i;
best_count = count;
}
}
}
if (found) {
cls->select_literal(target);
return;
}
diff_literal_selection::operator()(cls);
}
void max_no_selection::operator()(clause * cls) {
unsigned num_lits = cls->get_num_literals();
for (unsigned i = 0; i < num_lits; i++) {
literal const & l1 = cls->get_literal(i);
if (!l1.sign()) {
unsigned j = 0;
for (; j < num_lits; j++) {
if (i != j) {
literal const & l2 = cls->get_literal(j);
if (!greater(m_order, l1, l2))
break;
}
}
if (j == num_lits)
return; // clause has maximal positive literal.
}
}
diff_literal_selection::operator()(cls);
}
};