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adding factorization

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This commit is contained in:
Nikolaj Bjorner 2021-03-26 12:20:51 -07:00
parent a352a6638a
commit c2b353ba72
2 changed files with 86 additions and 1 deletions
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82
src/math/dd/dd_pdd.cpp
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@ -30,6 +30,8 @@ namespace dd {
m_dmark_level = 0;
m_disable_gc = false;
m_is_new_node = false;
if (s == mod2N_e && power_of_2 == 1)
s = mod2_e;
m_semantics = s;
m_mod2N = rational::power_of_two(power_of_2);
m_power_of_2 = power_of_2;
@ -685,12 +687,61 @@ namespace dd {
return p;
}
/**
* factor p into lc*v^degree + rest
* such that degree(rest, v) < degree
* Initial implementation is very naive
* - memoize intermediary results
*/
void pdd_manager::factor(pdd const& p, unsigned v, unsigned degree, pdd& lc, pdd& rest) {
unsigned level_v = m_var2level[v];
if (degree == 0) {
lc = p;
rest = zero();
}
else if (level(p.root) < level_v) {
lc = zero();
rest = p;
}
else if (level(p.root) > level_v) {
pdd lc1 = zero(), rest1 = zero();
pdd vv = mk_var(p.var());
factor(p.hi(), v, degree, lc, rest);
factor(p.lo(), v, degree, lc1, rest1);
lc += lc1;
rest += rest1;
lc *= vv;
rest *= vv;
}
else {
unsigned d = 0;
pdd r = p;
while (d < degree && !r.is_val() && level(r.root) == level_v) {
d++;
r = r.hi();
}
if (d == degree) {
lc = r;
r = p;
rest = zero();
pdd pow = one();
for (unsigned i = 0; i < degree; r = r.hi(), pow *= mk_var(v), ++i)
rest += pow * r.lo();
}
else {
lc = zero();
rest = p;
}
}
}
bool pdd_manager::is_linear(pdd const& p) {
return is_linear(p.root);
}
/*
Determine whether p is a binary polynomials
Determine whether p is a binary polynomial
of the form v1, x*v1 + v2, or x*v1 + y*v2 + v3
where v1, v2 are values.
*/
@ -952,6 +1003,35 @@ namespace dd {
return m_degree[p];
}
unsigned pdd_manager::degree(PDD p, unsigned v) {
init_mark();
unsigned level_v = level(v);
unsigned max_d = 0, d = 0;
m_todo.push_back(p);
while (!m_todo.empty()) {
PDD r = m_todo.back();
if (is_marked(r))
m_todo.pop_back();
else if (is_val(r))
m_todo.pop_back();
else if (level(r) < level_v)
m_todo.pop_back();
else if (level(r) == level_v) {
d = 1;
while (!is_val(hi(r)) && level(hi(r)) == level_v) {
++d;
r = hi(r);
}
max_d = std::max(d, max_d);
m_todo.pop_back();
}
else
m_todo.push_back(lo(r)).push_back(hi(r));
}
return max_d;
}
double pdd_manager::tree_size(pdd const& p) {
init_mark();