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better encodings for at-most-1, #755

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2016-10-10 23:46:03 -07:00
parent 5d9820f3e2
commit 8d2b70a5e2
17 changed files with 232 additions and 253 deletions
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52
src/util/sorting_network.h
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@ -201,7 +201,11 @@ Notes:
if (dualize(k, n, xs, in)) {
return ge(full, k, n, in.c_ptr());
}
else if (k == 1) {
return mk_at_most_1(full, n, xs);
}
else {
std::cout << "sort " << k << "\n";
SASSERT(2*k <= n);
m_t = full?LE_FULL:LE;
card(k + 1, n, xs, out);
@ -230,6 +234,54 @@ Notes:
private:
literal mk_at_most_1(bool full, unsigned n, literal const* xs) {
literal_vector in(n, xs);
literal result = ctx.fresh();
unsigned inc_size = 4;
while (!in.empty()) {
literal_vector ors;
unsigned i = 0;
unsigned n = in.size();
bool last = n <= inc_size;
for (; i + inc_size < n; i += inc_size) {
mk_at_most_1_small(full, last, inc_size, in.c_ptr() + i, result, ors);
}
if (i < n) {
mk_at_most_1_small(full, last, n - i, in.c_ptr() + i, result, ors);
}
if (last) {
break;
}
in.reset();
in.append(ors);
ors.reset();
}
return result;
}
void mk_at_most_1_small(bool full, bool last, unsigned n, literal const* xs, literal result, literal_vector& ors) {
if (!last) {
literal ex = ctx.fresh();
for (unsigned j = 0; j < n; ++j) {
add_clause(ctx.mk_not(xs[j]), ex);
}
if (full) {
literal_vector lits(n, xs);
lits.push_back(ctx.mk_not(ex));
add_clause(lits.size(), lits.c_ptr());
}
ors.push_back(ex);
}
for (unsigned i = 0; i < n; ++i) {
for (unsigned j = i + 1; j < n; ++j) {
add_clause(ctx.mk_not(result), ctx.mk_not(xs[i]), ctx.mk_not(xs[j]));
}
if (full) {
add_clause(result, xs[i]);
}
}
}
std::ostream& pp(std::ostream& out, unsigned n, literal const* lits) {
for (unsigned i = 0; i < n; ++i) ctx.pp(out, lits[i]) << " ";
return out;