update vendor/

vendor/github.com/crillab/gophersat/solver/clause_alloc.go

@@ -0,0 +1,29 @@
+package solver
+
+// This file deals with an attempt for an efficient clause allocator/deallocator, to relax GC's work.
+
+const (
+	nbLitsAlloc = 5000000 // How many literals are initialized at first?
+)
+
+type allocator struct {
+	lits    []Lit // A list of lits, that will be sliced to make []Lit
+	ptrFree int   // Index of the first free item in lits
+}
+
+var alloc allocator
+
+// newLits returns a slice of lits containing the given literals.
+// It is taken from the preinitialized pool if possible,
+// or is created from scratch.
+func (a *allocator) newLits(lits ...Lit) []Lit {
+	if a.ptrFree+len(lits) > len(a.lits) {
+		a.lits = make([]Lit, nbLitsAlloc)
+		copy(a.lits, lits)
+		a.ptrFree = len(lits)
+		return a.lits[:len(lits)]
+	}
+	copy(a.lits[a.ptrFree:], lits)
+	a.ptrFree += len(lits)
+	return a.lits[a.ptrFree-len(lits) : a.ptrFree]
+}