Avoid running lb algos without satisfied requirements

bnb/bnb.cpp

@@ -29,31 +29,28 @@ solver::solver(graph& g, lb lb_algorithm) : graph_(g), partition_(partition{g}),
 }
 
 unsigned int solver::get_lower(){
-	unsigned int lower_bound;
+    std::vector<node_id> sources, sinks;
+	for(node_id node = 1; node <= graph_.num_nodes(); node++){
+		if(partition_.assigned_subgraph_of(node) == partition::sg_a)
+			sources.push_back(node);
+		else if(partition_.assigned_subgraph_of(node) == partition::sg_b)
+			sinks.push_back(node);
+	}
+    if (sources.empty() || sinks.empty()) {
+        return partition_.current_objective();
+    }
+
+    
+
 	if(lb_algorithm_ == lb::ek){
-		std::vector<node_id> sources, sinks;
-		for(node_id node = 1; node <= graph_.num_nodes(); node++){
-			if(partition_.assigned_subgraph_of(node) == partition::sg_a)
-				sources.push_back(node);
-			else if(partition_.assigned_subgraph_of(node) == partition::sg_b)
-				sinks.push_back(node);
-		}	
 		auto ek = edmonds_karp(graph_, sources, sinks);
 		ek.run();
-		lower_bound = ek.get_max_flow();
+	    return ek.get_max_flow();
 	}
 	else if(lb_algorithm_ == lb::ibfs){
-		std::vector<node_id> sources, sinks;
-		for(node_id node = 1; node <= graph_.num_nodes(); node++){
-			if(partition_.assigned_subgraph_of(node) == partition::sg_a)
-				sources.push_back(node);
-			else if(partition_.assigned_subgraph_of(node) == partition::sg_b)
-				sinks.push_back(node);
-		}	
 		auto i_bfs = incremental_bfs(graph_, sources, sinks);
 		i_bfs.run();
-		lower_bound = i_bfs.get_max_flow();
-
+		return i_bfs.get_max_flow();
 	}
 	else if(lb_algorithm_ == lb::pr){
 
@@ -61,11 +58,7 @@ unsigned int solver::get_lower(){
 	else if(lb_algorithm_ == lb::gp){
 
 	}
-	else{
-		lower_bound = partition_.current_objective();
-	}
-
-	return lower_bound;
+    return partition_.current_objective();
 }
 
 void solver::solve() {