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model based opt dev

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2016-04-28 09:47:55 -07:00
parent 83d84dcedd
commit 932ef442ae
3 changed files with 239 additions and 133 deletions

View file

@ -20,6 +20,25 @@ Revision History:
#include "model_based_opt.h"
std::ostream& operator<<(std::ostream& out, opt::bound_type bt) {
switch (bt) {
case opt::unbounded: return out << "unbounded";
case opt::strict: return out << "strict";
case opt::non_strict: return out << "non-strict";
}
return out;
}
std::ostream& operator<<(std::ostream& out, opt::ineq_type ie) {
switch (ie) {
case opt::t_eq: return out << " = ";
case opt::t_lt: return out << " < ";
case opt::t_le: return out << " <= ";
}
return out;
}
namespace opt {
@ -33,17 +52,16 @@ namespace opt {
bool model_based_opt::invariant() {
// variables in each row are sorted.
for (unsigned i = 0; i < m_rows.size(); ++i) {
if (!invariant(m_rows[i])) {
if (!invariant(i, m_rows[i])) {
return false;
}
}
return true;
}
bool model_based_opt::invariant(row const& r) {
bool model_based_opt::invariant(unsigned index, row const& r) {
rational val = r.m_coeff;
vector<var> const& vars = r.m_vars;
SASSERT(!vars.empty());
for (unsigned i = 0; i < vars.size(); ++i) {
var const& v = vars[i];
SASSERT(i + 1 == vars.size() || v.m_id < vars[i+1].m_id);
@ -52,8 +70,8 @@ namespace opt {
}
SASSERT(val == r.m_value);
SASSERT(r.m_type != t_eq || val.is_zero());
SASSERT(r.m_type != t_lt || val.is_neg());
SASSERT(r.m_type != t_le || !val.is_pos());
SASSERT(index == 0 || r.m_type != t_lt || val.is_neg());
SASSERT(index == 0 || r.m_type != t_le || !val.is_pos());
return true;
}
@ -83,31 +101,34 @@ namespace opt {
SASSERT(invariant());
unsigned_vector other;
while (!objective().m_vars.empty()) {
var const& v = objective().m_vars.back();
TRACE("opt", tout << "tableau\n";);
var v = objective().m_vars.back();
unsigned x = v.m_id;
rational const& coeff = v.m_coeff;
rational const& x_val = m_var2value[x];
unsigned_vector const& row_ids = m_var2row_ids[x];
unsigned bound_index;
unsigned bound_row_index;
rational bound_coeff;
other.reset();
if (find_bound(x, bound_index, other, coeff.is_pos())) {
rational bound_coeff = m_rows[bound_index].m_coeff;
if (find_bound(x, bound_row_index, bound_coeff, other, coeff.is_pos())) {
row& r = m_rows[bound_row_index];
SASSERT(!bound_coeff.is_zero());
for (unsigned i = 0; i < other.size(); ++i) {
resolve(other[i], bound_coeff, bound_index, x);
resolve(bound_row_index, bound_coeff, other[i], x);
}
// coeff*x + objective -> coeff*(bound) + objective
multiply(coeff/bound_coeff, bound_index);
SASSERT(invariant(m_rows[bound_index]));
objective().m_vars.back().m_coeff.reset();
add(m_objective_id, bound_index);
SASSERT(invariant(objective()));
m_rows[bound_index].m_alive = false;
// coeff*x + objective <= ub
// a2*x + t2 <= 0
// => coeff*x <= -t2*coeff/a2
// objective + t2*coeff/a2 <= ub
mul_add(m_objective_id, - coeff/bound_coeff, bound_row_index);
m_rows[bound_row_index].m_alive = false;
}
else {
return unbounded;
}
}
value = objective().m_coeff;
value = objective().m_value;
if (objective().m_type == t_lt) {
return strict;
}
@ -116,8 +137,8 @@ namespace opt {
}
}
bool model_based_opt::find_bound(unsigned x, unsigned& bound_index, unsigned_vector& other, bool is_pos) {
bound_index = UINT_MAX;
bool model_based_opt::find_bound(unsigned x, unsigned& bound_row_index, rational& bound_coeff, unsigned_vector& other, bool is_pos) {
bound_row_index = UINT_MAX;
rational lub_val;
rational const& x_val = m_var2value[x];
unsigned_vector const& row_ids = m_var2row_ids[x];
@ -126,32 +147,39 @@ namespace opt {
row& r = m_rows[row_id];
if (r.m_alive) {
rational a = get_coefficient(row_id, x);
if (a.is_pos() == is_pos) {
rational value = r.m_value - x_val*a; // r.m_value = val_x*a + val(t), val(t) := r.m_value - val_x*a;
if (bound_index == UINT_MAX) {
if (a.is_zero()) {
// skip
}
else if (a.is_pos() == is_pos) {
rational value = x_val - (r.m_value/a);
if (bound_row_index == UINT_MAX) {
lub_val = value;
bound_index = row_id;
bound_row_index = row_id;
bound_coeff = a;
}
else if ((is_pos && value < lub_val) || (!is_pos && value > lub_val)) {
other.push_back(bound_index);
other.push_back(bound_row_index);
lub_val = value;
bound_index = row_id;
bound_row_index = row_id;
bound_coeff = a;
}
else {
other.push_back(bound_index);
else if (bound_row_index != row_id) {
other.push_back(row_id);
}
}
else if (!a.is_zero()) {
else {
r.m_alive = false;
}
}
}
return bound_index != UINT_MAX;
return bound_row_index != UINT_MAX;
}
rational model_based_opt::get_coefficient(unsigned row_id, unsigned var_id) {
row const& r = m_rows[row_id];
SASSERT(!r.m_vars.empty());
if (r.m_vars.empty()) {
return rational::zero();
}
unsigned lo = 0, hi = r.m_vars.size();
while (lo < hi) {
unsigned mid = lo + (hi - lo)/2;
@ -177,7 +205,22 @@ namespace opt {
}
}
// v0 - v1 <= 0
// v0 - v2 <= 0
// v2 >= v1
// -> v1 - v2 <= 0
//
// t1 + a1*x <= 0
// t2 + a2*x <= 0
// (t2 + a2*x) <= (t1 + a1*x)*a2/a1
// => t2*a1/a2 - t1 <= 0
// => t2 - t1*a2/a1 <= 0
bool model_based_opt::resolve(unsigned row_id1, rational const& a1, unsigned row_id2, unsigned x) {
SASSERT(a1 == get_coefficient(row_id1, x));
SASSERT(!a1.is_zero());
// row1 is of the form a1*x + t1 <~ 0
// row2 is of the form a2*x + t2 <~ 0
// assume that a1, a2 have the same sign.
@ -194,38 +237,20 @@ namespace opt {
if (a2.is_zero()) {
return false;
}
else if (a1.is_pos() && a2.is_pos()) {
multiply(-a1/a2, row_id2);
add(row_id2, row_id1);
if (a1.is_pos() == a2.is_pos()) {
mul_add(row_id2, -a2/a1, row_id1);
return true;
}
else if (a1.is_neg() && a2.is_neg()) {
NOT_IMPLEMENTED_YET();
// tbd
return true;
}
else {
m_rows[row_id2].m_alive = false;
return false;
}
}
void model_based_opt::multiply(rational const& c, unsigned row_id) {
if (c.is_one()) {
return;
}
row& r = m_rows[row_id];
SASSERT(r.m_alive);
for (unsigned i = 0; i < r.m_vars.size(); ++i) {
r.m_vars[i].m_coeff *= c;
}
r.m_coeff *= c;
r.m_value *= c;
}
// add row2 to row1, store result in row1.
void model_based_opt::add(unsigned row_id1, unsigned row_id2) {
//
// set row1 <- row1 + c*row2
//
void model_based_opt::mul_add(unsigned row_id1, rational const& c, unsigned row_id2) {
m_new_vars.reset();
row& r1 = m_rows[row_id1];
row const& r2 = m_rows[row_id2];
@ -233,75 +258,82 @@ namespace opt {
for(; i < r1.m_vars.size() || j < r2.m_vars.size(); ) {
if (j == r2.m_vars.size()) {
m_new_vars.append(r1.m_vars.size() - i, r1.m_vars.c_ptr() + i);
break;
}
else if (i == r1.m_vars.size()) {
if (i == r1.m_vars.size()) {
for (; j < r2.m_vars.size(); ++j) {
m_new_vars.push_back(r2.m_vars[j]);
m_new_vars.back().m_coeff *= c;
if (row_id1 != m_objective_id) {
m_var2row_ids[r2.m_vars[j].m_id].push_back(row_id1);
}
}
break;
}
unsigned v1 = r1.m_vars[i].m_id;
unsigned v2 = r2.m_vars[j].m_id;
if (v1 == v2) {
m_new_vars.push_back(r1.m_vars[i]);
m_new_vars.back().m_coeff += c*r2.m_vars[j].m_coeff;
++i;
++j;
if (m_new_vars.back().m_coeff.is_zero()) {
m_new_vars.pop_back();
}
}
else if (v1 < v2) {
m_new_vars.push_back(r1.m_vars[i]);
++i;
}
else {
unsigned v1 = r1.m_vars[i].m_id;
unsigned v2 = r2.m_vars[j].m_id;
if (v1 == v2) {
m_new_vars.push_back(r1.m_vars[i]);
m_new_vars.back().m_coeff += r2.m_vars[j].m_coeff;
++i;
++j;
if (m_new_vars.back().m_coeff.is_zero()) {
m_new_vars.pop_back();
}
m_new_vars.push_back(r2.m_vars[j]);
m_new_vars.back().m_coeff *= c;
if (row_id1 != m_objective_id) {
m_var2row_ids[r2.m_vars[j].m_id].push_back(row_id1);
}
else if (v1 < v2) {
m_new_vars.push_back(r1.m_vars[i]);
++i;
}
else {
m_new_vars.push_back(r2.m_vars[j]);
if (row_id1 != m_objective_id) {
m_var2row_ids[r2.m_vars[j].m_id].push_back(row_id1);
}
++j;
}
}
++j;
}
}
r1.m_coeff += r2.m_coeff;
r1.m_coeff += c*r2.m_coeff;
r1.m_vars.swap(m_new_vars);
r1.m_value += r2.m_value;
r1.m_value += c*r2.m_value;
if (r2.m_type == t_lt) {
r1.m_type = t_lt;
}
SASSERT(invariant(r1));
SASSERT(invariant(row_id1, r1));
}
void model_based_opt::display(std::ostream& out) const {
for (unsigned i = 0; i < m_rows.size(); ++i) {
display(out, m_rows[i]);
}
for (unsigned i = 0; i < m_var2row_ids.size(); ++i) {
unsigned_vector const& rows = m_var2row_ids[i];
out << i << ": ";
for (unsigned j = 0; j < rows.size(); ++j) {
out << rows[j] << " ";
}
out << "\n";
}
}
void model_based_opt::display(std::ostream& out, row const& r) const {
vector<var> const& vars = r.m_vars;
out << (r.m_alive?"+":"-") << " ";
for (unsigned i = 0; i < vars.size(); ++i) {
if (i > 0 && vars[i].m_coeff.is_pos()) {
out << "+ ";
}
out << vars[i].m_coeff << "* v" << vars[i].m_id << " ";
}
out << r.m_coeff;
switch (r.m_type) {
case t_eq:
out << " = 0\n";
break;
case t_lt:
out << " < 0\n";
break;
case t_le:
out << " <= 0\n";
break;
if (r.m_coeff.is_pos()) {
out << " + " << r.m_coeff << " ";
}
else if (r.m_coeff.is_neg()) {
out << r.m_coeff << " ";
}
out << r.m_type << " 0; value: " << r.m_value << "\n";
}
unsigned model_based_opt::add_var(rational const& value) {
@ -311,7 +343,8 @@ namespace opt {
return v;
}
void model_based_opt::set_row(row& r, vector<var> const& coeffs, rational const& c, ineq_type rel) {
void model_based_opt::set_row(unsigned row_id, vector<var> const& coeffs, rational const& c, ineq_type rel) {
row& r = m_rows[row_id];
rational val(c);
SASSERT(r.m_vars.empty());
r.m_vars.append(coeffs.size(), coeffs.c_ptr());
@ -323,23 +356,21 @@ namespace opt {
r.m_coeff = c;
r.m_value = val;
r.m_type = rel;
SASSERT(invariant(r));
SASSERT(invariant(row_id, r));
}
void model_based_opt::add_constraint(vector<var> const& coeffs, rational const& c, ineq_type rel) {
rational val(c);
row r0;
rational val(c);
unsigned row_id = m_rows.size();
m_rows.push_back(r0);
row& r = m_rows.back();
set_row(r, coeffs, c, rel);
m_rows.push_back(row());
set_row(row_id, coeffs, c, rel);
for (unsigned i = 0; i < coeffs.size(); ++i) {
m_var2row_ids[coeffs[i].m_id].push_back(row_id);
}
}
void model_based_opt::set_objective(vector<var> const& coeffs, rational const& c) {
set_row(objective(), coeffs, c, t_le);
set_row(m_objective_id, coeffs, c, t_le);
}
}

View file

@ -37,6 +37,8 @@ namespace opt {
strict,
non_strict
};
class model_based_opt {
public:
@ -67,22 +69,20 @@ namespace opt {
vector<var> m_new_vars;
bool invariant();
bool invariant(row const& r);
bool invariant(unsigned index, row const& r);
row& objective() { return m_rows[0]; }
bool find_bound(unsigned x, unsigned& bound_index, unsigned_vector& other, bool is_pos);
bool find_bound(unsigned x, unsigned& bound_index, rational& bound_coeff, unsigned_vector& other, bool is_pos);
rational get_coefficient(unsigned row_id, unsigned var_id);
bool resolve(unsigned row_id1, rational const& a1, unsigned row_id2, unsigned x);
void multiply(rational const& c, unsigned row_id);
void mul_add(unsigned row_id1, rational const& c, unsigned row_id2);
void add(unsigned row_id1, unsigned row_id2);
void set_row(row& r, vector<var> const& coeffs, rational const& c, ineq_type rel);
void set_row(unsigned row_id, vector<var> const& coeffs, rational const& c, ineq_type rel);
public:
@ -112,4 +112,8 @@ namespace opt {
}
std::ostream& operator<<(std::ostream& out, opt::bound_type bt);
std::ostream& operator<<(std::ostream& out, opt::ineq_type ie);
#endif

View file

@ -1,49 +1,120 @@
#include "model_based_opt.h"
typedef opt::model_based_opt::var var;
static void add_ineq(opt::model_based_opt& mbo, unsigned x, int a, unsigned y, int b, int k, opt::ineq_type rel) {
vector<var> vars;
vars.push_back(var(x, rational(a)));
vars.push_back(var(y, rational(b)));
mbo.add_constraint(vars, rational(k), rel);
}
static void add_ineq(opt::model_based_opt& mbo, unsigned x, int a, int k, opt::ineq_type rel) {
vector<var> vars;
vars.push_back(var(x, rational(a)));
mbo.add_constraint(vars, rational(k), rel);
}
// test with upper bounds
static void test1() {
opt::model_based_opt mbo;
typedef opt::model_based_opt::var var;
vector<var> vars;
unsigned x = mbo.add_var(rational(2));
unsigned y = mbo.add_var(rational(3));
unsigned z = mbo.add_var(rational(4));
unsigned u = mbo.add_var(rational(5));
vars.reset();
vars.push_back(var(x, rational(1)));
vars.push_back(var(y, rational(-1)));
mbo.add_constraint(vars, rational(0), opt::t_le);
vars.reset();
vars.push_back(var(x, rational(1)));
vars.push_back(var(z, rational(-1)));
mbo.add_constraint(vars, rational(0), opt::t_le);
vars.reset();
vars.push_back(var(y, rational(1)));
vars.push_back(var(u, rational(-1)));
mbo.add_constraint(vars, rational(0), opt::t_le);
vars.reset();
vars.push_back(var(z, rational(1)));
vars.push_back(var(u, rational(-1)));
mbo.add_constraint(vars, rational(-1), opt::t_le);
vars.reset();
vars.push_back(var(u, rational(1)));
mbo.add_constraint(vars, rational(4), opt::t_le);
add_ineq(mbo, x, 1, y, -1, 0, opt::t_le);
add_ineq(mbo, x, 1, z, -1, 0, opt::t_le);
add_ineq(mbo, y, 1, u, -1, 0, opt::t_le);
add_ineq(mbo, z, 1, u, -1, 1, opt::t_le);
add_ineq(mbo, u, 1, -6, opt::t_le);
vars.reset();
vars.push_back(var(x, rational(2)));
mbo.set_objective(vars, rational(0));
rational value;
opt::bound_type bound = mbo.maximize(value);
opt::bound_type bound = mbo.maximize(value);
std::cout << bound << ": " << value << "\n";
}
// test with lower bounds
static void test2() {
opt::model_based_opt mbo;
vector<var> vars;
unsigned x = mbo.add_var(rational(5));
unsigned y = mbo.add_var(rational(4));
unsigned z = mbo.add_var(rational(3));
unsigned u = mbo.add_var(rational(2));
add_ineq(mbo, x, -1, y, 1, 0, opt::t_le);
add_ineq(mbo, x, -1, z, 1, 0, opt::t_le);
add_ineq(mbo, y, -1, u, 1, 0, opt::t_le);
add_ineq(mbo, z, -1, u, 1, 1, opt::t_le);
add_ineq(mbo, u, -1, -6, opt::t_le);
vars.reset();
vars.push_back(var(x, rational(-2)));
mbo.set_objective(vars, rational(0));
rational value;
opt::bound_type bound = mbo.maximize(value);
std::cout << bound << ": " << value << "\n";
}
// test unbounded
static void test3() {
opt::model_based_opt mbo;
vector<var> vars;
unsigned x = mbo.add_var(rational(2));
unsigned y = mbo.add_var(rational(3));
unsigned z = mbo.add_var(rational(4));
unsigned u = mbo.add_var(rational(5));
add_ineq(mbo, x, 1, y, -1, 0, opt::t_le);
add_ineq(mbo, x, 1, z, -1, 0, opt::t_le);
add_ineq(mbo, y, 1, u, -1, 0, opt::t_le);
add_ineq(mbo, z, 1, u, -1, 1, opt::t_le);
vars.reset();
vars.push_back(var(x, rational(2)));
mbo.set_objective(vars, rational(0));
rational value;
opt::bound_type bound = mbo.maximize(value);
std::cout << bound << ": " << value << "\n";
}
// test strict
static void test4() {
opt::model_based_opt mbo;
vector<var> vars;
unsigned x = mbo.add_var(rational(2));
unsigned y = mbo.add_var(rational(3));
unsigned z = mbo.add_var(rational(4));
unsigned u = mbo.add_var(rational(5));
add_ineq(mbo, x, 1, y, -1, 0, opt::t_lt);
add_ineq(mbo, x, 1, z, -1, 0, opt::t_lt);
add_ineq(mbo, y, 1, u, -1, 0, opt::t_le);
add_ineq(mbo, z, 1, u, -1, 1, opt::t_le);
add_ineq(mbo, u, 1, -6, opt::t_le);
vars.reset();
vars.push_back(var(x, rational(2)));
mbo.set_objective(vars, rational(0));
rational value;
opt::bound_type bound = mbo.maximize(value);
std::cout << bound << ": " << value << "\n";
}
// test with mix of upper and lower bounds
void tst_model_based_opt() {
test1();
test2();
test3();
test4();
}