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/*++
Copyright (c) 2020 Microsoft Corporation
Module Name:
int_gcd_test.h
Abstract:
Gcd_Test heuristic
gcd test
5*x + 3*y + 6*z = 5
suppose x is fixed at 2.
so we have 10 + 3(y + 2z) = 5
5 = -3(y + 2z)
this is unsolvable because 5/3 is not an integer.
so we create a lemma that rules out this condition.
Author:
Nikolaj Bjorner (nbjorner)
Lev Nachmanson (levnach)
Revision History:
--*/
#pragma once
#include "math/lp/lia_move.h"
namespace lp {
class int_solver;
class lar_solver;
class int_gcd_test {
struct parity {
mpq m_offset;
mpq m_modulo;
const row_strip* m_row = nullptr;
parity(mpq const& p, mpq const& m, row_strip const& r):
m_offset(p),
m_modulo(m),
m_row(&r)
{}
};
class int_solver& lia;
class lar_solver& lra;
unsigned m_next_gcd = 0;
unsigned m_delay = 0;
mpq m_consts;
mpq m_least_coeff;
mpq m_lcm_den;
unsigned_vector m_inserted_vars;
vector> m_parities;
unsigned_vector m_visited;
unsigned m_visited_ts = 0;
bool is_visited(unsigned i) { return m_visited.get(i, 0) == m_visited_ts; }
void mark_visited(unsigned i) { m_visited.setx(i, m_visited_ts, 0); }
void reset_test();
bool insert_parity(unsigned j, row_strip const& r, mpq const& parity, mpq const& modulo);
bool gcd_test();
bool gcd_test_for_row(const static_matrix> & A, unsigned i);
bool ext_gcd_test(const row_strip & row);
void fill_explanation_from_fixed_columns(const row_strip & row);
void add_to_explanation_from_fixed_or_boxed_column(unsigned j);
bool accumulate_parity(const row_strip & row, unsigned least_coeff_index);
public:
int_gcd_test(int_solver& lia);
lia_move operator()();
bool should_apply();
};
}