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simplify cheap_eqs

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2020-06-19 12:24:24 -07:00
parent e3503f060f
commit c4fbe05a96
2 changed files with 85 additions and 190 deletions
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1
src/math/lp/int_solver.cpp
View file

@ -515,6 +515,7 @@ std::ostream& int_solver::display_row_info(std::ostream & out, unsigned row_inde
return out;
}
bool int_solver::shift_var(unsigned j, unsigned range) {
if (is_fixed(j) || is_base(j))
return false;

274
src/math/lp/lp_bound_propagator.h
View file

@ -24,9 +24,8 @@ class lp_bound_propagator {
// and u, v reference the same column
class vertex {
unsigned m_row;
unsigned m_column; // in the row
unsigned m_column;
ptr_vector<vertex> m_children;
mpq m_offset; // offset from parent (parent - child = offset)
vertex* m_parent;
unsigned m_level; // the distance in hops to the root;
// it is handy to find the common ancestor
@ -36,11 +35,9 @@ class lp_bound_propagator {
vertex() {}
vertex(unsigned row,
unsigned column,
const mpq & offset,
bool neg) :
m_row(row),
m_column(column),
m_offset(offset),
m_parent(nullptr),
m_level(0),
m_neg(neg)
@ -49,8 +46,6 @@ class lp_bound_propagator {
unsigned row() const { return m_row; }
vertex* parent() const { return m_parent; }
unsigned level() const { return m_level; }
const mpq& offset() const { return m_offset; }
mpq& offset() { return m_offset; }
bool neg() const { return m_neg; }
bool& neg() { return m_neg; }
void add_child(vertex* child) {
@ -64,7 +59,7 @@ class lp_bound_propagator {
out << "r = " << m_row << ", c = " << m_column << ", P = {";
if (m_parent) { tout << "(" << m_parent->row() << ", " << m_parent->column() << ")";}
else { tout << "null"; }
tout << "} , offs = " << m_offset << ", lvl = " << m_level << (neg()? " -":" +");
tout << "} , lvl = " << m_level << (neg()? " -":" +");
return out;
}
bool operator==(const vertex& o) const {
@ -235,7 +230,7 @@ public:
}
bool set_sign_and_column(signed_column& i, const row_cell<mpq> & c) {
bool set_sign_and_column(signed_column& i, const row_cell<mpq> & c) const {
if (c.coeff().is_one()) {
i.sign() = false;
i.column() = c.var();
@ -248,12 +243,19 @@ public:
}
return false;
}
const mpq& val(unsigned j) const {
return lp().get_column_value(j).x;
}
const mpq& val(const vertex* v) const {
return val(v->column());
}
void try_add_equation_with_fixed_tables(vertex *v) {
SASSERT(m_fixed_vertex);
unsigned v_j = v->column();
unsigned j;
if (!lp().find_in_fixed_tables(v->offset(), is_int(v_j), j))
if (!lp().find_in_fixed_tables(val(v_j), is_int(v_j), j))
return;
TRACE("cheap_eq", tout << "found j=" << j << " for v=";
v->print(tout) << "\n in lp.fixed tables\n";);
@ -280,10 +282,9 @@ public:
return tree_contains_r(m_root, v);
}
vertex * alloc_v(unsigned row_index, unsigned column, const mpq& offset, bool neg) {
vertex * v = alloc(vertex, row_index, column, offset, neg);
vertex * alloc_v(unsigned row_index, unsigned column, bool neg) {
vertex * v = alloc(vertex, row_index, column, neg);
SASSERT(!tree_contains(v));
SASSERT(!m_fixed_vertex || !neg);
return v;
}
@ -292,33 +293,22 @@ public:
TRACE("cheap_eq", tout << "ddd = " << lp().settings().ddd << "\n";);
SASSERT(!m_root && !m_fixed_vertex);
signed_column x, y;
mpq offset;
TRACE("cheap_eq", display_row_info(row_index, tout););
if (!is_tree_offset_row(row_index, x, y, offset))
TRACE("cheap_eq", print_row(tout, row_index););
if (!is_tree_offset_row(row_index, x, y)) {
TRACE("cheap_eq", tout << "not an offset row\n";);
return;
if (x.sign()) { // make the coeff before x positive
offset.neg();
if (y.is_set()) {
y.sign() = !y.sign();
}
x.sign() = false;
}
const mpq& r = val(x.column());
m_root = alloc_v(row_index, x.column(), false);
if (y.not_set()) {
// x + offset = 0
m_root = alloc_v(row_index, x.column(), -offset, false);
set_fixed_vertex(m_root);
return;
set_fixed_vertex(m_root);
} else {
bool neg = x.sign() == y.sign();
vertex *v = alloc_v(row_index, y.column(), neg);
m_root->add_child(v);
}
// create root with the offset zero
m_root = alloc_v( row_index, x.column(), mpq(0), false);
// we have x + y.sign() * y + offset = 0
// x.offset is set to zero as x plays the role of m_root
// if sign_y = true then y.offset() = offset + x.offset()
// else (!y.sign())*y = x + offset, so neg = !y.sign()
bool neg = !y.sign();
vertex *v = alloc_v( row_index, y.column(), offset, neg);
m_root->add_child(v);
// keep root in the positive table
m_offset_to_verts.insert(r, m_root);
}
unsigned column(unsigned row, unsigned index) {
@ -327,98 +317,34 @@ public:
bool fixed_phase() const { return m_fixed_vertex; }
vertex * add_child_from_row_continue_fixed(vertex *v, signed_column& y, const mpq& offset) {
SASSERT(!v->neg());
mpq y_offs = y.sign()? v->offset() + offset: - v->offset() - offset;
vertex *vy = alloc_v(v->row(), y.column(), y_offs, false);
v->add_child(vy);
return v;
}
vertex *add_child_from_row_continue(vertex *v, signed_column& y, const mpq& offset) {
if (fixed_phase())
return add_child_from_row_continue_fixed(v, y, offset);
// create a vertex for y
// see the explanation below
mpq y_offs = v->neg()? - v->offset() - offset: v->offset() + offset;
bool neg = v->neg() ^ y.sign();
vertex *vy = alloc_v(v->row(), y.column(), y_offs, neg);
v->add_child(vy);
return v;
#if 0
if (v->neg()) { // have to use -x
// it means that v->offset is the distance of -x from the root
if (y.sign()) {
// we have x - y + offset = 0, or y = x + offset, or -y = -x - offset
neg = true;
y_offs = - v->offset() - offset;
} else {
// we have x + y + offset = 0, or -y = x + offset, or y = -x - offset
neg = false;
y_offs = - v->offset() - offset;
}
} else {
SASSERT(!v->neg()); // have to use x
if (y.sign()) {
// we have x - y + offset = 0, or y = x + offset
neg = false;
y_offs = v->offset() + offset;
} else {
// we have x + y + offset = 0, or -y = x + offset
neg = true;
y_offs = v->offset() + offset;
}
}
#endif
}
// returns the vertex to start exploration from, or nullptr
// parent->column() is present in the row
// Returns the vertex to start exploration from, or nullptr.
// It is assumed that parent->column() is present in the row
vertex* add_child_from_row(unsigned row_index, vertex* parent) {
TRACE("cheap_eq", display_row_info(row_index, tout););
TRACE("cheap_eq", print_row(tout, row_index););
signed_column x, y;
mpq offset;
if (!is_tree_offset_row(row_index, x, y, offset)) {
if (!is_tree_offset_row(row_index, x, y)) {
TRACE("cheap_eq", tout << "not an offset row\n"; );
return nullptr;
}
if (y.not_set()) {
// x.sign() * x + offset = 0
SASSERT(parent->column() == x.column());
mpq offs = x.sign()? offset: -offset;
if (fixed_phase()) {
// now the neg, the last argument, is false since all offsets are
// absolute
vertex* v = alloc_v( row_index, x.column(), offs , false);
parent->add_child(v);
TRACE("cheap_eq", tout << "fixed phase, adding v = "; v->print(tout) << "\n"; );
return v;
}
vertex *v = alloc_v( row_index, x.column(), parent->offset(), false);
vertex *v = alloc_v( row_index, x.column(), parent->neg());
parent->add_child(v);
set_fixed_vertex(v);
switch_to_fixed_mode_in_tree(m_root, offs - parent->offset());
TRACE("cheap_eq", tout << "after switching to fixed phase, adding v = "; v->print(tout) << "\n"; );
return v;
}
SASSERT(x.is_set() && y.is_set());
// v is exactly like parent, but the row is different
vertex *v = alloc_v(row_index, parent->column(), parent->offset(), parent->neg());
vertex *v = alloc_v(row_index, parent->column(), parent->neg());
parent->add_child(v);
SASSERT(x.column() == v->column() || y.column() == v->column());
if (y.column() == v->column()) {
std::swap(x, y); // we want x.column() to be the some as v->column() for convenience
}
if (x.sign()) {
x.sign() = false;
y.sign() = !y.sign();
offset.neg(); // now we have x +-y + offset = 0
}
vertex * t = add_child_from_row_continue(v, y, offset);
TRACE("cheap_eq", tout << "not a fixed phase, adding t = "; t->print(tout) << "\n"; );
return t;
unsigned col = v->column() == y.column()? x.column(): y.column();
bool neg = x.sign() == y.sign() ? !v->neg(): v->neg();
vertex *vy = alloc_v(v->row(), col, neg);
v->add_child(vy);
return v;
}
bool is_equal(lpvar j, lpvar k) const {
@ -427,49 +353,23 @@ public:
void check_for_eq_and_add_to_offset_table(vertex* v, map<mpq, vertex*, obj_hash<mpq>, mpq_eq>& table) {
vertex *k; // the other vertex
if (table.find(v->offset(), k)) {
if (table.find(val(v), k)) {
TRACE("cheap_eq", tout << "found k " ; k->print(tout) << "\n";);
if (k->column() != v->column() &&
!is_equal(k->column(), v->column()))
report_eq(k, v);
} else {
TRACE("cheap_eq", tout << "registered offset " << v->offset() << " to { "; v->print(tout) << "} \n";);
table.insert(v->offset(), v);
TRACE("cheap_eq", tout << "registered: " << val(v) << " -> { "; v->print(tout) << "} \n";);
table.insert(val(v), v);
}
}
void check_for_eq_and_add_to_offsets(vertex* v) {
TRACE("cheap_eq_det", v->print(tout) << "\n";);
if (!fixed_phase()) {
if (!v->neg() && v->offset().is_zero()) {
if (m_root->column() != v->column() &&
!is_equal(m_root->column(), v->column()))
report_eq(m_root, v);
} else if (v->neg())
check_for_eq_and_add_to_offset_table(v, m_offset_to_verts_neg);
else
check_for_eq_and_add_to_offset_table(v, m_offset_to_verts);
}
else { // m_fixed_vertex is not nullptr - all offsets are absolute
SASSERT(v->neg() == false);
unsigned j;
unsigned v_col = v->column();
if (lp().find_in_fixed_tables(v->offset(), is_int(v_col), j)) {
if (j != v_col) {
explanation ex;
constraint_index lc, uc;
lp().get_bound_constraint_witnesses_for_column(j, lc, uc);
ex.push_back(lc);
ex.push_back(uc);
explain_fixed_in_row(v->row(), ex);
TRACE("cheap_eq", display_row_info(v->row(), tout););
add_eq_on_columns(ex, v_col, j);
}
}
check_for_eq_and_add_to_offset_table(v, m_offset_to_verts);
}
if (v->neg())
check_for_eq_and_add_to_offset_table(v, m_offset_to_verts_neg);
else
check_for_eq_and_add_to_offset_table(v, m_offset_to_verts);
}
void clear_for_eq() {
@ -484,7 +384,7 @@ public:
for (vertex* k : path) {
k->print(out) << "\n";
if (k->row() != pr) {
display_row_info(pr = k->row(), out);
print_row(out, pr = k->row());
}
}
return out;
@ -549,7 +449,7 @@ public:
}
void cheap_eq_table(unsigned rid) {
TRACE("cheap_eqs", tout << "checking if row " << rid << " can propagate equality.\n"; display_row_info(rid, tout););
TRACE("cheap_eqs", tout << "checking if row " << rid << " can propagate equality.\n"; print_row(tout, rid););
unsigned x, y;
mpq k;
if (is_offset_row(rid, x, y, k)) {
@ -603,8 +503,8 @@ public:
TRACE("arith_eq", tout << "propagate eq two rows:\n";
tout << "x : v" << x << "\n";
tout << "x2 : v" << x2 << "\n";
display_row_info(rid, tout);
display_row_info(row_id, tout););
print_row(tout, rid);
print_row(tout, row_id););
add_eq_on_columns(ex, x, x2);
}
return;
@ -646,10 +546,7 @@ public:
}
std::ostream& display_row_of_vertex(vertex* k, std::ostream& out) const {
return display_row_info(k->row(), out );
}
std::ostream& display_row_info(unsigned r, std::ostream& out) const {
return lp().get_int_solver()->display_row_info(out, r);
return print_row(out, k->row());
}
void find_path_on_tree(ptr_vector<vertex> & path, vertex* u, vertex* v) const {
@ -676,9 +573,6 @@ public:
SASSERT(u->level() == v->level());
TRACE("cheap_eq_details", tout << "u = " ;u->print(tout); tout << "\nv = ";v->print(tout) << "\n";);
while (u != v) {
if (u->row() == v->row() && u->offset() == v->offset()) // we have enough explanation now
break;
up = u->parent();
vp = v->parent();
if (up->row() == u->row())
@ -746,6 +640,9 @@ public:
TRACE("cheap_eq", tout << "tree = "; print_tree(tout, m_root) << "\n";);
SASSERT(tree_is_correct());
explore_under(m_root);
if (fixed_phase()) {
create_fixed_eqs(m_root);
}
TRACE("cheap_eq", tout << "done for row_index " << row_index << "\n";);
TRACE("cheap_eq", tout << "tree size = " << verts_size(););
delete_tree(m_root);
@ -755,6 +652,35 @@ public:
m_offset_to_verts_neg.reset();
}
void create_fixed_eqs(vertex* v) {
try_add_equation_with_fixed_tables(v);
for (vertex* c: v->children())
try_add_equation_with_fixed_tables(c);
}
std::ostream& print_row(std::ostream & out, unsigned row_index) const {
signed_column x, y;
if (true || !is_tree_offset_row(row_index, x, y))
return lp().get_int_solver()->display_row_info(out, row_index);
bool first = true;
for (const auto &c: lp().A_r().m_rows[row_index]) {
if (lp().column_is_fixed(c.var()))
continue;
if (c.coeff().is_one()) {
if (!first)
out << "+";
}
else if (c.coeff().is_minus_one())
out << "-";
out << lp().get_variable_name(c.var()) << " ";
first = false;
}
out << "\n";
return out;
}
void set_fixed_vertex(vertex *v) {
TRACE("cheap_eq", if (v) v->print(tout); else tout << "set m_fixed_vertex to nullptr"; tout << "\n";);
m_fixed_vertex = v;
@ -811,34 +737,11 @@ public:
}
}
void switch_to_fixed_mode_in_tree(vertex *v, const mpq& new_v_offset) {
SASSERT(v);
set_fixed_vertex(v);
mpq delta = new_v_offset - v->offset();
switch_to_fixed_mode(m_root, delta);
SASSERT(v->offset() == new_v_offset);
m_offset_to_verts_neg.reset();
m_offset_to_verts.reset();
}
void switch_to_fixed_mode(vertex *v, const mpq& d) {
v->offset() += d;
if (v->neg()) {
v->offset() = - v->offset();
v->neg() = false;
}
for (vertex * c : v->children()) {
switch_to_fixed_mode(c, d);
}
}
// In case of only one non fixed column, and the function returns true,
// this column would be represened by x.
bool is_tree_offset_row(
unsigned row_index,
bool is_tree_offset_row( unsigned row_index,
signed_column & x,
signed_column & y,
mpq& offset) {
signed_column & y) const {
const auto & row = lp().get_row(row_index);
for (unsigned k = 0; k < row.size(); k++) {
const auto& c = row[k];
@ -853,16 +756,7 @@ public:
} else
return false;
}
if (x.not_set() && y.not_set())
return false;
offset = mpq(0);
for (const auto& c : row) {
if (column_is_fixed(c.var()))
offset += c.coeff() * get_lower_bound_rational(c.var());
}
return true;
return x.is_set() || y.is_set();
}
};
}