\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 update integrates inferences to smt.arith.solver=6 related to grobner basis computation and handling of div/mod axioms to reconcile performance with smt.arith.solver=2.
The default of smt.arth.nl.grobner_subs_fixed is changed to 1 to make comparison with solver=2 more direct.
The selection of cluster equalities for solver=6 was reconciled with how it is done for solver=2.
* remove the bound on total iterations in simplex
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* remove unncesseray checks in get_freedom_interval_for_column()
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* fix the build of test-z3
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* Revert "remove unncesseray checks in get_freedom_interval_for_column()"
This reverts commit 6770ed85e3.
* optimize get_freedom_interval_for_column() for feasible case
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* add function lar_solver::status_feasible
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* rename status_is_feasible() to is_feasible()
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* fix the linux build
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
there are some different sources for the performance regression illustrated by the example. The mitigations will be enabled separately:
- m_bv_to_propagate is too expensive
- lp_bound_propagator misses equalities in two different ways:
- it resets row checks after backtracking even though they could still propagate
- it misses equalities for fixed rows when the fixed constant value does not correspond to a fixed variable.
FYI @levnach
bugs in:
- rewriting of 0-ary expressions was incomplete
- sharing annotations when a node has two theories attached it is shared
- sharing of const of an array
Remove unreadable part of pretty printer for lp solver.
