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find minimal deltas in patching

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2023-07-01 07:48:07 -07:00
parent f5d9ffaca1
commit 61948fa1ff
2 changed files with 57 additions and 64 deletions
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54
src/math/lp/int_solver.cpp
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@ -70,9 +70,9 @@ namespace lp {
// clang-format on
/**
* \brief find integral and minimal, in the absolute values, deltas such that x - alpha*delta is integral too.
*/
*/
bool get_patching_deltas(const rational& x, const rational& alpha,
rational& delta_0, rational& delta_1) {
rational& delta_plus, rational& delta_minus) {
auto a1 = numerator(alpha);
auto a2 = denominator(alpha);
auto x1 = numerator(x);
@ -102,36 +102,21 @@ namespace lp {
// << x + (a1 / a2) * (-u * t) * x1 << std::endl;
lp_assert((x + (a1 / a2) * (-u * t) * x1).is_int());
// 1 = (u- l*x2 ) * a1 + (v + l*a1)*x2, for every integer l.
rational l_low, l_high;
auto sign = u.is_pos() ? 1 : -1;
auto p = sign * floor(abs(u / x2));
auto p_ = p + sign;
lp_assert(p * x2 <= u && u <= p_ * x2 || p * x2 >= u && u >= p_ * x2);
// std::cout << "u = " << u << ", v = " << v << std::endl;
// std::cout << "p = " << p << ", p_ = " << p_ << std::endl;
// std::cout << "u - p*x2 = " << u - p * x2 << ", u - p_*x2 = " << u - p_ * x2
// << std::endl;
mpq d_0 = (u - p * x2) * t * x1;
mpq d_1 = (u - p_ * x2) * t * x1;
if (abs(d_0) < abs(d_1)) {
delta_0 = d_0;
delta_1 = d_1;
} else {
delta_0 = d_1;
delta_1 = d_0;
}
rational d = u * t * x1;
delta_plus = mod(d, a2);
lp_assert(delta_plus > 0);
delta_minus = delta_plus - a2;
lp_assert(delta_minus < 0);
return true;
// std::cout << "delta_0 = " << delta_0 << std::endl;
// std::cout << "delta_1 = " << delta_1 << std::endl;
}
// clang-format off
/**
* \brief try to patch the basic column v
*/
bool int_solver::patcher::patch_basic_column_on_row_cell(unsigned v, row_cell<mpq> const& c) {
if (v == c.var())
return false;
if (!lra.column_is_int(c.var())) // could use real to patch integer
if (!lra.column_is_int(c.var())) // could use real to patch integer
return false;
if (c.coeff().is_int())
return false;
@ -139,19 +124,20 @@ namespace lp {
mpq r = fractional_part(lra.get_value(v));
lp_assert(0 < r && r < 1);
lp_assert(0 < a && a < 1);
mpq delta_0, delta_1;
if (!get_patching_deltas(r, a, delta_0, delta_1))
mpq delta_plus, delta_minus;
if (!get_patching_deltas(r, a, delta_plus, delta_minus))
return false;
if (try_patch_column(v, c.var(), delta_0))
return true;
if (try_patch_column(v, c.var(), delta_1))
return true;
return false;
if (lia.random() % 2) {
return try_patch_column(v, c.var(), delta_plus) ||
try_patch_column(v, c.var(), delta_minus);
} else {
return try_patch_column(v, c.var(), delta_minus) ||
try_patch_column(v, c.var(), delta_plus);
}
}
// clang-format off
bool int_solver::patcher::try_patch_column(unsigned v, unsigned j, mpq const& delta) {
const auto & A = lra.A_r();
if (delta < 0) {