Add support for NodeCount attribute (#110)

Author: odow

src/MOI_wrapper.jl

@@ -1777,13 +1777,12 @@ function MOI.get(model::Optimizer, ::MOI.BarrierIterations)
     return Int64(p[])
 end
 
-# TODO(odow): missing an upstream method for this.
-# function MOI.get(model::Optimizer, ::MOI.NodeCount)
-#     p = Ref{Int64}(0)
-#     ret = Highs_getLongInfoValue(model, "mip_node_count", p)
-#     _check_ret(ret)
-#     return p[]
-# end
+function MOI.get(model::Optimizer, ::MOI.NodeCount)
+    p = Ref{Int64}(0)
+    ret = Highs_getInt64InfoValue(model, "mip_node_count", p)
+    _check_ret(ret)
+    return p[]
+end
 
 function MOI.get(
     model::Optimizer,

test/MOI_wrapper.jl

@@ -267,6 +267,14 @@ function test_SimplexIterations_BarrierIterations()
     @test MOI.get(model, MOI.BarrierIterations()) > 0
 end
 
+function test_NodeCount()
+    model = _knapsack_model(mip = true, solver = "choose")
+    @test MOI.get(model, MOI.NodeCount()) == 0
+    MOI.optimize!(model)
+    @test MOI.get(model, MOI.NodeCount()) > 0
+    return
+end
+
 end
 
 TestMOIHighs.runtests()