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Tune Grobner equations

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\brief convert p == 0 into a solved form v == r, such that
   v has bounds [lo, oo) iff r has bounds [lo', oo)
   v has bounds (oo,hi]  iff r has bounds (oo,hi']

   The solved form allows the Grobner solver identify more bounds conflicts.
   A bad leading term can miss bounds conflicts.
   For example for x + y + z == 0 where x, y : [0, oo) and z : (oo,0]
   we prefer to solve z == -x - y instead of x == -z - y
   because the solution -z - y has neither an upper, nor a lower bound.

The Grobner solver is augmented with a notion of a substitution that is applied before the solver is run.
This commit is contained in:
Nikolaj Bjorner 2022-07-11 16:14:26 -07:00
parent f33c933241
commit 316ed778e0
5 changed files with 127 additions and 13 deletions
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4
src/math/lp/nla_core.h
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@ -466,7 +466,9 @@ public:
void display_matrix_of_m_rows(std::ostream & out) const;
void set_active_vars_weights(nex_creator&);
unsigned get_var_weight(lpvar) const;
void add_row_to_grobner(const vector<lp::row_cell<rational>> & row);
void add_row_to_grobner(const vector<lp::row_cell<rational>> & row);
bool is_solved(dd::pdd const& p, unsigned& v, dd::pdd& r);
void add_eq_to_grobner(dd::pdd& p, u_dependency* dep);
bool check_pdd_eq(const dd::solver::equation*);
const rational& val_of_fixed_var_with_deps(lpvar j, u_dependency*& dep);
dd::pdd pdd_expr(const rational& c, lpvar j, u_dependency*&);