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optimise rewrite_eqs to avoid fresh variables

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2025-01-29 15:37:00 -08:00 • committed by Lev Nachmanson
parent ed3df333b3
commit 058b9e4a6d
1 changed files with 29 additions and 16 deletions
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45
src/math/lp/dioph_eq.cpp
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@ -923,6 +923,7 @@ namespace lp {
const auto & row = m_e_matrix.m_rows[ei];
for (const auto& p : row) {
if (m_k2s.has_key(p.var())) {
/*
std::cout << "entry:" << ei << " belongs to f but depends on column " << p.var() << std::endl;
std::cout << "m_var_register.local_to_external(p.var()):" << m_var_register.local_to_external(p.var()) << std::endl;
print_entry(ei, std::cout);
@ -933,7 +934,8 @@ namespace lp {
std::cout << std::endl;
std::cout << "column " << p.var() << " is subst by entry:";
print_entry(m_k2s[p.var()],std::cout) << std::endl;
print_entry(m_k2s[p.var()],std::cout) << std::endl;
*/
return false;
}
}
@ -2190,6 +2192,9 @@ namespace lp {
// returns true if an equlity was rewritten and false otherwise
bool rewrite_eqs() {
unsigned h = -1;
unsigned n = 0; // number of choices for a fresh variable
mpq the_smallest_ahk;
unsigned kh, kh_sign;
for (unsigned ei=0; ei < m_e_matrix.row_count(); ei++) {
if (belongs_to_s(ei)) continue;
if (m_e_matrix.m_rows[ei].size() == 0) {
@ -2200,23 +2205,31 @@ namespace lp {
return false;
}
}
h = ei;
break;
}
if (h == UINT_MAX)
return false;
auto [ahk, k, k_sign] = find_minimal_abs_coeff(h);
TRACE("dioph_eq", tout << "eh:"; print_entry(h, tout);
tout << "ahk:" << ahk << ", k:" << k << ", k_sign:" << k_sign
<< std::endl;);
auto [ahk, k, k_sign] = find_minimal_abs_coeff(ei);
if (ahk.is_one()) {
TRACE("dioph_eq", tout << "push to S:\n"; print_entry(ei, tout););
move_entry_from_f_to_s(k, ei);
eliminate_var_in_f(ei, k, k_sign);
return true;
}
if (ahk.is_one()) {
TRACE("dioph_eq", tout << "push to S:\n"; print_entry(h, tout););
move_entry_from_f_to_s(k, h);
eliminate_var_in_f(h, k, k_sign);
} else {
fresh_var_step(h, k, ahk * mpq(k_sign));
if (n == 0 || the_smallest_ahk > ahk) {
n = 1;
the_smallest_ahk = ahk;
h = ei;
kh = k;
kh_sign = k_sign;
continue;
}
if (the_smallest_ahk == ahk && lra.settings().random_next() % (++n) == 0) {
h = ei;
kh = k;
kh_sign = k_sign;
}
}
if (h == UINT_MAX) return false;
SASSERT(!the_smallest_ahk.is_one());
fresh_var_step(h, kh, the_smallest_ahk * mpq(kh_sign));
return true;
}