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propagate cheap eqs

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2020-06-02 12:38:31 -07:00
parent 865dfe0590
commit 1e4e887221
5 changed files with 78 additions and 82 deletions

62
src/math/lp/bound_analyzer_on_row.h
View file

@ -13,9 +13,8 @@ Abstract:
In the same loop trying to pin variables by pushing the partial sum up, denoting the variable related to it by _l
Author:
Lev Nachmanson (levnach)
Lev Nachmanson (levnach)
Nikolaj Bjorner (nbjorner)
Revision History:
@ -31,7 +30,7 @@ template <typename C, typename B> // C plays a role of a container, B - lp_bound
class bound_analyzer_on_row {
const C& m_row;
B & m_bp;
unsigned m_row_or_term_index;
unsigned m_row_index;
int m_column_of_u; // index of an unlimited from above monoid
// -1 means that such a value is not found, -2 means that at least two of such monoids were found
int m_column_of_l; // index of an unlimited from below monoid
@ -48,7 +47,7 @@ public :
:
m_row(it),
m_bp(bp),
m_row_or_term_index(row_or_term_index),
m_row_index(row_or_term_index),
m_column_of_u(-1),
m_column_of_l(-1),
m_rs(rs)
@ -62,7 +61,7 @@ public :
B & bp) {
bound_analyzer_on_row a(row, bj, rs, row_or_term_index, bp);
a.analyze();
// TBD: a.analyze_eq();
a.analyze_eq();
}
private:
@ -84,37 +83,6 @@ private:
limit_all_monoids_from_above();
}
void analyze_eq() {
lpvar x = null_lpvar, y = null_lpvar;
for (const auto & c : m_row) {
if (m_bp.get_column_type(c.var()) == column_type::fixed)
continue;
if (x == null_lpvar && c.coeff().is_one())
x = c.var();
else if (y == null_lpvar && c.coeff().is_minus_one())
y = c.var();
else
return;
}
if (x == null_lpvar || y == null_lpvar)
return;
impq value;
for (const auto & c : m_row) {
if (m_bp.get_column_type(c.var()) == column_type::fixed)
value += c.coeff() * lb(c.var());
}
if (!value.is_zero()) {
// insert / check offset table to infer equalities
// of the form y = z from offset table collision:
// value = (x - y)
// value = (x - z)
}
else {
// m_bp.try_add_fixed(x, y, m_row_or_term_index);
}
}
bool bound_is_available(unsigned j, bool lower_bound) {
return (lower_bound && lower_bound_is_available(j)) ||
(!lower_bound && upper_bound_is_available(j));
@ -327,7 +295,7 @@ private:
// }
void limit_j(unsigned j, const mpq& u, bool coeff_before_j_is_pos, bool is_lower_bound, bool strict){
m_bp.try_add_bound(u, j, is_lower_bound, coeff_before_j_is_pos, m_row_or_term_index, strict);
m_bp.try_add_bound(u, j, is_lower_bound, coeff_before_j_is_pos, m_row_index, strict);
}
void advance_u(unsigned j) {
@ -361,6 +329,24 @@ private:
}
}
void analyze_eq() {
unsigned x = UINT_MAX, y = UINT_MAX;
unsigned k = 0;
for (const auto& c : m_row) {
if (!m_bp.lp().column_is_fixed(c.var())) {
if (x == UINT_MAX && c.coeff().is_one())
x = k;
else if (y == UINT_MAX && c.coeff().is_minus_one())
y = k;
else
return;
}
k++;
}
if (x == UINT_MAX || y == UINT_MAX)
return;
m_bp.try_create_eq(x, y, m_row_index);
}
};
}

2
src/math/lp/indexed_vector.h
View file

@ -83,7 +83,7 @@ public:
return m_data.size();
}
unsigned size() {
unsigned size() const {
return m_index.size();
}

46
src/math/lp/lar_solver.h
View file

@ -161,20 +161,7 @@ class lar_solver : public column_namer {
bool use_lu() const;
bool sizes_are_correct() const;
bool implied_bound_is_correctly_explained(implied_bound const & be, const vector<std::pair<mpq, unsigned>> & explanation) const;
template <typename T>
void analyze_new_bounds_on_row(
unsigned row_index,
lp_bound_propagator<T>& bp) {
lp_assert(!use_tableau());
unsigned j = m_mpq_lar_core_solver.m_r_basis[row_index]; // basis column for the row
bound_analyzer_on_row<indexed_vector<mpq>, lp_bound_propagator<T>>::analyze_row(
m_mpq_lar_core_solver.get_pivot_row(),
j,
zero_of_type<numeric_pair<mpq>>(),
row_index,
bp);
}
template <typename T>
void analyze_new_bounds_on_row_tableau(
unsigned row_index,
@ -196,17 +183,8 @@ class lar_solver : public column_namer {
void substitute_basis_var_in_terms_for_row(unsigned i);
template <typename T>
void calculate_implied_bounds_for_row(unsigned i, lp_bound_propagator<T> & bp) {
if (use_tableau()) {
analyze_new_bounds_on_row_tableau(i, bp);
} else {
m_mpq_lar_core_solver.calculate_pivot_row(i);
substitute_basis_var_in_terms_for_row(i);
analyze_new_bounds_on_row(i, bp);
}
}
template <typename T>
void propagate_bounds_on_a_term(const lar_term& t, lp_bound_propagator<T> & bp, unsigned term_offset) {
NOT_IMPLEMENTED_YET();
SASSERT(use_tableau());
analyze_new_bounds_on_row_tableau(i, bp);
}
static void clean_popped_elements(unsigned n, u_set& set);
static void shrink_inf_set_after_pop(unsigned n, u_set & set);
@ -346,28 +324,14 @@ public:
void activate(constraint_index ci);
void random_update(unsigned sz, var_index const * vars);
template <typename T>
void propagate_bounds_on_terms(lp_bound_propagator<T> & bp) {
for (unsigned i = 0; i < m_terms.size(); i++) {
if (term_is_used_as_row(i))
continue; // this term is used a left side of a constraint,
// it was processed as a touched row if needed
propagate_bounds_on_a_term(*m_terms[i], bp, i);
}
}
template <typename T>
void propagate_bounds_for_touched_rows(lp_bound_propagator<T> & bp) {
if (!use_tableau())
return; // todo: consider to remove the restriction
SASSERT(use_tableau());
for (unsigned i : m_rows_with_changed_bounds) {
calculate_implied_bounds_for_row(i, bp);
if (settings().get_cancel_flag())
return;
}
m_rows_with_changed_bounds.clear();
if (!use_tableau()) {
propagate_bounds_on_terms(bp);
}
}
bool is_fixed(column_index const& j) const { return column_is_fixed(j); }
inline column_index to_column_index(unsigned v) const { return column_index(external_to_column_index(v)); }
@ -591,7 +555,7 @@ public:
return false;
}
void round_to_integer_solution();
inline const row_strip<mpq> & get_row(unsigned i) { return A_r().m_rows[i]; }
inline const row_strip<mpq> & get_row(unsigned i) const { return A_r().m_rows[i]; }
bool row_is_correct(unsigned i) const;
bool ax_is_correct() const;
bool get_equality_and_right_side_for_term_on_current_x(tv const& t, mpq &rs, constraint_index& ci, bool &upper_bound) const;

49
src/math/lp/lp_bound_propagator.h
View file

@ -1,18 +1,40 @@
/*
Copyright (c) 2017 Microsoft Corporation
Author: Lev Nachmanson
Author:
Nickolaj Bjorner (nbjorner)
Lev Nachmanson (levnach)
*/
#pragma once
#include "math/lp/lp_settings.h"
namespace lp {
template <typename T>
class lp_bound_propagator {
// defining a graph on columns x, y such that there is a row x - y = c, where c is a constant
struct vertex {
unsigned m_row;
unsigned m_index; // in the row
bool m_sign; // true if the vertex plays the role of y
vector<unsigned> m_adjacent_edges; // points to the
vertex(unsigned row, unsigned index) : m_row(row), m_index(index) {}
};
// an edge can be between columns in the same row or between two different rows in the same column
struct edge {
unsigned m_a;
unsigned m_b;
impq m_offset;
};
vector<vertex> m_vertices;
vector<edge> m_edges;
std::unordered_map<unsigned, unsigned> m_improved_lower_bounds; // these maps map a column index to the corresponding index in ibounds
std::unordered_map<unsigned, unsigned> m_improved_upper_bounds;
T& m_imp;
public:
vector<implied_bound> m_ibounds;
lp_bound_propagator(T& imp): m_imp(imp) {}
const lar_solver& lp() const { return m_imp.lp(); }
column_type get_column_type(unsigned j) const {
return m_imp.lp().get_column_type(j);
}
@ -65,5 +87,30 @@ public:
void consume(const mpq& a, constraint_index ci) {
m_imp.consume(a, ci);
}
void create_initial_xy(unsigned x, unsigned y, unsigned row_index) {
impq value;
const auto& row = lp().get_row(row_index);
for (unsigned k = 0; k < row.size(); k++) {
if (k == x || k == y)
continue;
const auto& c = row[k];
value += c.coeff() * lp().get_lower_bound(c.var());
}
vertex xv(row_index, x);
m_vertices.push_back(xv);
vertex yv(row_index, y);
m_vertices.push_back(yv);
NOT_IMPLEMENTED_YET();
}
void try_create_eq(unsigned x, unsigned y, unsigned row_index) {
m_vertices.clear();
m_edges.clear();
create_initial_xy(x, y, row_index);
NOT_IMPLEMENTED_YET();
}
};
}

1
src/smt/theory_lra.cpp
View file

@ -4033,4 +4033,3 @@ template class lp::lp_bound_propagator<smt::theory_lra::imp>;
template void lp::lar_solver::propagate_bounds_for_touched_rows<smt::theory_lra::imp>(lp::lp_bound_propagator<smt::theory_lra::imp>&);
template void lp::lar_solver::explain_implied_bound<smt::theory_lra::imp>(lp::implied_bound&, lp::lp_bound_propagator<smt::theory_lra::imp>&);
template void lp::lar_solver::calculate_implied_bounds_for_row<smt::theory_lra::imp>(unsigned int, lp::lp_bound_propagator<smt::theory_lra::imp>&);
template void lp::lar_solver::propagate_bounds_on_terms<smt::theory_lra::imp>(lp::lp_bound_propagator<smt::theory_lra::imp>&);