Merge pull request #55 from OptimalBranching/xz/ipmis

add ip solver for mis problem

Author: ArrogantGao

lib/OptimalBranchingMIS/src/OptimalBranchingMIS.jl

@@ -16,6 +16,7 @@ export TensorNetworkSolver
 export NumOfVertices, D3Measure
 
 export mis_size, mis_branch_count
+export ip_mis
 export counting_mis1, counting_mis2, counting_xiao2013
 
 include("types.jl")

lib/OptimalBranchingMIS/src/algorithms/algorithms.jl

@@ -30,4 +30,4 @@ include("mis1.jl")
 include("mis2.jl")
 include("xiao2013.jl")
 include("xiao2013_utils.jl")
-
+include("ip.jl")

lib/OptimalBranchingMIS/src/algorithms/ip.jl

@@ -0,0 +1,15 @@
+using OptimalBranchingCore.JuMP, OptimalBranchingCore.HiGHS
+
+function ip_mis(g::AbstractGraph; optimizer=HiGHS.Optimizer, verbose::Bool=false)
+    model = Model(optimizer)
+    !verbose && set_silent(model)
+    n = nv(g)
+    @variable(model, 0 <= x[i = 1:n] <= 1, Int)
+    @objective(model, Max, sum(x))
+    for e in edges(g)
+        @constraint(model, x[src(e)] + x[dst(e)] <= 1)
+    end
+    optimize!(model)
+    @assert is_solved_and_feasible(model)
+    return Int(round(sum(value.(x))))
+end

lib/OptimalBranchingMIS/test/mis.jl

@@ -1,6 +1,7 @@
 using EliminateGraphs, EliminateGraphs.Graphs
 using Test, Random
 
+using OptimalBranchingMIS
 using OptimalBranchingMIS: find_children, unconfined_vertices, is_line_graph, first_twin, twin_filter!, short_funnel_filter!, desk_filter!, effective_vertex, all_three_funnel, all_four_funnel, rho, optimal_four_cycle, optimal_vertex, has_fine_structure, count_o_path, closed_neighbors, is_complete_graph
 
 function graph_from_edges(edges)
@@ -168,6 +169,7 @@ end
         mis_size_mis1 = counting_mis1(g).size
         mis_size_mis2 = counting_mis2(g).size
         mis_size_xiao = counting_xiao2013(g).size
-        @test mis_size_standard == mis_size_mis1 == mis_size_mis2 == mis_size_xiao
+        mis_size_ip = ip_mis(g)
+        @test mis_size_standard == mis_size_mis1 == mis_size_mis2 == mis_size_xiao == mis_size_ip
     end
 end