activity,initialization: order by variable

Instead of using the search order 1, N, N-1, N-2, ..., have the solver
use the order 1, 2, 3, 4, ... by default. This order maps better to the
way formulas are typically generated. The first variables correspond to
the variables of the input problem, which empirically results in a
quicker exploration of the input search space.

Signed-off-by: Norbert Manthey <[email protected]>

minisat/core/Solver.cc

@@ -94,7 +94,7 @@ static IntOption opt_ccmin_mode(_cat,
                                 IntRange(0, 3));
 static IntOption
 opt_phase_saving(_cat, "phase-saving", "Controls the level of phase saving (0=none, 1=limited, 2=full)", 2, IntRange(0, 2));
-static IntOption opt_init_act(_cat, "rnd-init", "Initial activity is 0:0, 1:random, 2:1000/v, 3:v", 0, IntRange(0, 3));
+static IntOption opt_init_act(_cat, "rnd-init", "Initial activity is 0:0, 1:random, 2:1000/v, 3:v", 2, IntRange(0, 3));
 static IntOption opt_init_act_init(_cat, "rnd-init-init", "Initial activity for rnd-init=2", 1000, IntRange(1, INT32_MAX));
 static IntOption opt_restart_first(_cat, "rfirst", "The base restart interval", 100, IntRange(1, INT32_MAX));
 static IntOption opt_restart_strategy(_cat, "restart", "How to schedule restarts (split,luby,dynamic)", 1, IntRange(1, 3));