func ordered(db *db.DB, a *assignment.Assignment) (l *cnf.Lit) {
// find the first in-order unassigned literal
for i := uint(1); i <= a.Len(); i++ {
if p, _ := a.Get(i); p == guess.Unassigned {
return &cnf.Lit{i, cnf.Pos}
}
}
return &cnf.Lit{0, 0}
}
func (lc *LitCounts) GetNextVmtf(a *assignment.Assignment) (l *cnf.Lit) {
var lit uint
for i := range lc.vmtf {
if lc.vmtf[i].lit < 0 {
lit = uint(-1 * lc.vmtf[i].lit)
} else {
lit = uint(lc.vmtf[i].lit)
}
if val, err := a.Get(lit); val == guess.Unassigned && err == nil {
if lc.vmtf[i].lit < 0 {
return &cnf.Lit{uint(lc.vmtf[i].lit * -1), cnf.Pos}
} else {
return &cnf.Lit{uint(lc.vmtf[i].lit), cnf.Pos}
}
}
}
panic("getNextVmtf is broken")
}
// We'll use a modified MOMS rule that only looks at binary clauses
func moms(db *db.DB, a *assignment.Assignment) (l *cnf.Lit) {
var (
counts = make([]int, a.Guess().Len())
eCount int
vals [2]uint
g = a.Guess()
biggest = 0
biggestI = -1
)
// Count up the total lits in binary clauses
for e := db.Learned; e != nil; e = e.Next {
eCount = 0
for _, l := range e.Clause.Lits {
if v, _ := g.Get(l.Val); v == guess.Unassigned {
eCount++
if eCount > 2 {
break
}
vals[eCount-1] = l.Val
}
}
if eCount <= 2 {
for i := 0; i < eCount; i++ {
counts[vals[i]-1]++
}
}
}
// Search for the biggest
for i, v := range counts {
if v > biggest {
biggest = v
biggestI = i
}
}
if biggestI == -1 {
return random(db, a)
} else {
return &cnf.Lit{uint(biggestI + 1), byte((rand.Int() % 2) + 1)}
}
panic("MOMS is broken")
}
func random(db *db.DB, a *assignment.Assignment) (l *cnf.Lit) {
sign := byte((rand.Int() % 2) + 1)
val := uint((rand.Int() % int(a.Len())) + 1)
for i := val; i <= a.Len(); i++ {
if v, _ := a.Get(i); v == guess.Unassigned {
return &cnf.Lit{i, sign}
}
}
for i := uint(1); i < val; i++ {
if v, _ := a.Get(i); v == guess.Unassigned {
return &cnf.Lit{i, sign}
}
}
return &cnf.Lit{0, 0}
}
func DpllTimeout(cdb *db.DB, a *assignment.Assignment, b *Brancher, m *db.Manager, adapt *Adapter, timeout <-chan time.Time) *guess.Guess {
nVar := a.Guess().Len()
aStack := make([]dpllStackNode, nVar)
top := -1
for {
top++
aStack[top].l = b.Decide(cdb, a)
aStack[top].Flipped = false
a.PushAssign(aStack[top].l.Val, aStack[top].l.Pol)
for {
select {
case <-timeout:
return nil
default:
}
status := cdb.Bcp(a.Guess(), *aStack[top].l, m)
if status == db.Conflict {
// BackTrack
for aStack[top].Flipped == true {
top--
a.PopAssign()
}
if top < 0 {
return nil
}
// Flip the assignment
a.PopAssign()
aStack[top].l.Flip()
aStack[top].Flipped = true
a.PushAssign(aStack[top].l.Val, aStack[top].l.Pol)
// Reconfigure if neccessary
if adapt != nil {
adapt.Reconfigure(cdb, b, m)
}
} else if status == db.Sat {
return a.Guess()
} else {
break
}
}
}
panic("Dpll is broken")
}
func vsids(db *db.DB, a *assignment.Assignment) (l *cnf.Lit) {
l = db.Counts.Max(a.Guess())
return
}