func (lc *LitCounts) Max(g *guess.Guess) *cnf.Lit {
var (
bestI int
bestV int
)
bestV = -1
for i, v := range lc.counts {
if int(v) > bestV {
if i < len(lc.counts)/2 { // negative polarity
if p, _ := g.Get(uint(i + 1)); p == guess.Unassigned {
bestV = int(v)
bestI = i
}
} else { // positive polarity
if p, _ := g.Get(uint(i - (len(lc.counts) / 2) + 1)); p == guess.Unassigned {
bestV = int(v)
bestI = i
}
}
}
}
if bestV == -1 {
return &cnf.Lit{0, 0}
} else if bestI < len(lc.counts)/2 {
return &cnf.Lit{uint(bestI + 1), guess.Neg}
} else {
return &cnf.Lit{uint(bestI + 1 - (len(lc.counts) / 2)), guess.Pos}
}
panic("LitCount.Max is horribly broken\n")
}
// View db as a queue. From the first 15/16 newest clauses, delete anything with
// more than 42 literals. From the last 1/16, delete anything with more than 8.
// This is a simplification of Berkmin. We'd need to add the notion of clause
// activity in order to do it properly. We'd also need restarts.
// Call it a TODO
func berkmin(cdb *DB, g *guess.Guess, m *Manager) {
var (
beginning = (g.NAssigned() / 16) * 15
count = 0
tmp *Entry
)
for e := cdb.Learned; e != nil; e = e.Next {
count++
if count > beginning {
if len(e.Clause.Lits) > 8 {
tmp = e.Prev
cdb.DelEntry(e)
e = tmp
}
} else {
if len(e.Clause.Lits) > 42 {
tmp = e.Prev
cdb.DelEntry(e)
e = tmp
}
}
}
}