fix #110. BaB should delete the already-split domains from the queue.

src/satisfiability/bab.jl

@@ -55,7 +55,7 @@ function output_bound(solver::BaB, problem::Problem, type::Symbol)
     doms = Tuple{Float64, Hyperrectangle}[(global_approx, problem.input)]
     index = ifelse(type == :max, 1, -1)
     while index * (global_approx - global_concrete) > solver.ϵ
-        dom = pick_out(doms) # pick_out implements the search strategy
+        dom, doms = pick_out(doms) # pick_out implements the search strategy
         subdoms = split_dom(dom[2]) # split implements the branching rule
         for i in 1:length(subdoms)
             dom_concrete, x = concrete_bound(nnet, subdoms[i], type) # Sample
@@ -74,7 +74,7 @@ end
 
 # Always pick the first dom
 function pick_out(doms)
-    return doms[1]
+    return (doms[1], doms[2:end])
 end
 
 function add_domain!(doms::Vector{Tuple{Float64, Hyperrectangle}}, new::Tuple{Float64, Hyperrectangle}, type::Symbol)