set the defalt for cheap_eqs=False, do not run

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

src/math/lp/lar_solver.h

@@ -366,8 +366,8 @@ class lar_solver : public column_namer {
         // these two loops should be run sequentially
         // since the first loop might change column bounds
         // and add fixed columns this way
-        bp.clear_for_eq();
         if (settings().cheap_eqs()) {
+            bp.clear_for_eq();
             for (unsigned i : m_rows_with_changed_bounds) {
                 calculate_cheap_eqs_for_row(i, bp);
                 if (settings().get_cancel_flag())

src/smt/params/smt_params_helper.pyg

@@ -49,7 +49,7 @@ def_module_params(module_name='smt',
                           ('bv.watch_diseq', BOOL, False, 'use watch lists instead of eager axioms for bit-vectors'),
                           ('bv.delay', BOOL, True, 'delay internalize expensive bit-vector operations'),
                           ('arith.random_initial_value', BOOL, False, 'use random initial values in the simplex-based procedure for linear arithmetic'),
-                          ('arith.cheap_eqs', BOOL, True, 'false - do not run, true - run cheap equality heuristic'),
+                          ('arith.cheap_eqs', BOOL, False, 'false - do not run, true - run cheap equality heuristic'),
                           ('arith.solver', UINT, 6, 'arithmetic solver: 0 - no solver, 1 - bellman-ford based solver (diff. logic only), 2 - simplex based solver, 3 - floyd-warshall based solver (diff. logic only) and no theory combination 4 - utvpi, 5 - infinitary lra, 6 - lra solver'),
                           ('arith.nl', BOOL, True, '(incomplete) nonlinear arithmetic support based on Groebner basis and interval propagation, relevant only if smt.arith.solver=2'),
                           ('arith.nl.nra', BOOL, True, 'call nra_solver when incremental lianirization does not produce a lemma, this option is ignored when arith.nl=false, relevant only if smt.arith.solver=6'),