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https://github.com/Z3Prover/z3
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update viable
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner
parent
a81a00a93c
commit
4d0f55febd
2 changed files with 18 additions and 120 deletions
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@ -63,7 +63,7 @@ namespace polysat {
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SASSERT(b1.is_val());
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SASSERT(b2.is_val());
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coeff = a1;
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coeff = a1.is_zero() ? a2 : a1;
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_backtrack.released = true;
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@ -77,12 +77,6 @@ namespace polysat {
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return true;
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#if 0
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if (match_linear4(c, a1, b1, e1, a2, b2, e2, out_interval, out_side_cond))
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return true;
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if (match_linear5(c, a1, b1, e1, a2, b2, e2, out_interval, out_side_cond))
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return true;
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#endif
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_backtrack.released = false;
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return false;
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}
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@ -230,110 +224,4 @@ namespace polysat {
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}
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return false;
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}
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#if 0
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/**
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* a1*y + e1 = 0, with a1 odd
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*/
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bool forbidden_intervals::match_linear4(signed_constraint const& c,
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rational & a1, pdd const& b1, pdd const& e1,
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rational & a2, pdd const& b2, pdd const& e2,
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eval_interval& interval, vector<signed_constraint>& side_cond) {
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if (a1.is_odd() && a2.is_zero() && b2.val().is_zero()) {
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push_eq(true, e2, side_cond);
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rational a_inv, pow2 = e1.manager().max_value() + 1;
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VERIFY(a1.mult_inverse(e1.manager().power_of_2(), a_inv));
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auto lo = -e1 * a_inv;
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auto lo_val = mod(-b1.val() * a_inv, pow2);
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auto hi = lo + 1;
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auto hi_val = mod(lo_val + 1, pow2);
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interval = to_interval(c, false, rational::one(), lo_val, lo, hi_val, hi);
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return true;
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}
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return false;
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}
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/**
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* Ad-hoc linear forbidden intervals
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* ax <= b, b != -1, a < b: x not in [ceil((b+1)/a) .. floor((2^K-1)/a)]
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* b <= ax, 0 < a < b: x not in [0 .. floor((b-1)/a)]
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* ax < b, a < b: x not in [ceil(b/a) .. floor((2^K-1)/a)]
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* b < ax, 0 < a <= b: x not in [0 .. floor(b/a)]
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*
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* TODO: generalize to ax + b <= c scenarios where ax does not overflow
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* and ax+b does not overflow, but is larger than c
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* Scenarios:
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* - ax + b <= c
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* - ax + b < c
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* - c <= ax + b
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* - c < ax + b
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*/
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bool forbidden_intervals::match_linear5(signed_constraint const& c,
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rational & a1, pdd const& b1, pdd const& e1,
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rational & a2, pdd const& b2, pdd const& e2,
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eval_interval& interval, vector<signed_constraint>& side_cond) {
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auto& m = e1.manager();
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// ax <= b, b != -1, a < b: x not in [ceil((b+1)/a) .. floor((2^K-1)/a)]
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if (c.is_positive() &&
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!a1.is_zero() && !a1.is_one() &&
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a2.is_zero() && b1.is_zero() && e2.is_val() &&
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a1 < b2.val() && b2.val() != m.max_value()) {
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if (!e1.is_val())
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side_cond.push_back(s.eq(e1));
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auto lo_val = ceil((b2.val() + 1) / a1);
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auto hi_val = floor(m.max_value() / a1) + 1;
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SASSERT(lo_val < hi_val);
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auto lo = m.mk_val(lo_val);
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auto hi = m.mk_val(hi_val);
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interval = eval_interval::proper(lo, lo_val, hi, hi_val);
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return true;
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}
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// b <= ax, 0 < a < b: x not in [0 .. floor((b-1)/a)]
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if (c.is_positive() &&
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!a2.is_zero() && !a2.is_one() &&
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a1.is_zero() && b2.is_zero() &&
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a2 < b1.val() && e1.is_val()) {
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if (!e2.is_val())
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side_cond.push_back(s.eq(e2));
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rational lo_val = rational::zero();
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rational hi_val = floor((b1.val() - 1) / a2) + 1;
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SASSERT(lo_val < hi_val);
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auto lo = m.mk_val(lo_val);
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auto hi = m.mk_val(hi_val);
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interval = eval_interval::proper(lo, lo_val, hi, hi_val);
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return true;
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}
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// ax < b, a < b: x not in [ceil(b/a) .. floor((2^K-1)/a)]
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if (c.is_negative() &&
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!a2.is_zero() && !a2.is_one() && b2.is_zero() &&
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a1.is_zero() && e1.is_val() && a2 < b1.val()) {
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if (!e2.is_val())
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side_cond.push_back(s.eq(e2));
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rational lo_val = ceil(b1.val() / a2);
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rational hi_val = floor(m.max_value() / a2) + 1;
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auto lo = m.mk_val(lo_val);
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auto hi = m.mk_val(hi_val);
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interval = eval_interval::proper(lo, lo_val, hi, hi_val);
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return true;
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}
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// b < ax, 0 < a <= b: x not in [0 .. floor(b/a)]
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if (c.is_negative() &&
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!a1.is_zero() && !a1.is_one() && b1.is_zero() &&
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a2.is_zero() && e2.is_val() && a1 <= b2.val()) {
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if (!e1.is_val())
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side_cond.push_back(s.eq(e2));
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rational lo_val = rational::zero();
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rational hi_val = floor(b2.val() / a1) + 1;
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auto lo = m.mk_val(lo_val);
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auto hi = m.mk_val(hi_val);
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interval = eval_interval::proper(lo, lo_val, hi, hi_val);
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return true;
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}
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return false;
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}
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#endif
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}
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@ -163,14 +163,20 @@ namespace polysat {
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/**
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* Traverse all interval constraints with coefficients to check whether current value 'val' for
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* 'v' is feasible. If not, extract a (maximal) interval to block 'v' from being assigned val.
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*
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* To investigate:
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* - side conditions are stronger than for unit intervals. They constrain the lower and upper bounds to
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* be precisely the assigned values. This is to ensure that lo/hi that are computed based on lo_val
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* and division with coeff are valid. Is there a more relaxed scheme?
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*/
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bool viable::refine_viable(pvar v, rational const& val) {
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auto* e = m_non_units[v];
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if (!e)
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return true;
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entry* first = e;
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rational const& max_value = s.var2pdd(v).max_value();
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do {
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rational coeff_val = mod(e->coeff * val, s.var2pdd(v).max_value() + 1);
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rational coeff_val = mod(e->coeff * val, max_value + 1);
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if (e->interval.currently_contains(coeff_val)) {
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rational delta_l = floor((coeff_val - e->interval.lo_val()) / e->coeff);
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rational delta_u = floor((e->interval.hi_val() - coeff_val - 1) / e->coeff);
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@ -181,21 +187,25 @@ namespace polysat {
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// pass
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}
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else if (e->interval.lo_val() <= coeff_val) {
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hi = val + 1;
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if (hi > s.var2pdd(v).max_value())
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rational lambda_u = floor((max_value - coeff_val - 1) / e->coeff);
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hi = val + lambda_u + 1;
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if (hi > max_value)
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hi = 0;
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}
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else {
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SASSERT(coeff_val < e->interval.hi_val());
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lo = val;
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rational lambda_l = floor(coeff_val / e->coeff);
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lo = val - lambda_l;
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}
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SASSERT(hi <= s.var2pdd(v).max_value());
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LOG("forbidden interval [" << lo << ", " << hi << "[\n");
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LOG("forbidden interval " << e->interval << " [" << lo << ", " << hi << "[");
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entry* ne = alloc_entry();
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ne->src = e->src;
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ne->side_cond = e->side_cond;
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ne->side_cond.push_back(s.eq(e->interval.hi(), e->interval.hi_val()));
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ne->side_cond.push_back(s.eq(e->interval.lo(), e->interval.lo_val()));
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ne->coeff = 1;
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pdd lop = s.var2pdd(v).mk_val(lo); // TODO?
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pdd lop = s.var2pdd(v).mk_val(lo);
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pdd hip = s.var2pdd(v).mk_val(hi);
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ne->interval = eval_interval::proper(lop, lo, hip, hi);
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intersect(v, ne);
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@ -435,7 +445,7 @@ namespace polysat {
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do {
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if (e->coeff != 1)
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out << e->coeff << " * v" << v << " ";
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out << e->interval << " " << e->side_cond << " " << e->src << " ";
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out << e->interval << " " << e->side_cond << " " << e->src << "; ";
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e = e->next();
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}
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while (e != first);
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