add hs13

Author: tmigot

test/nlp_problems/hs13.jl

@@ -0,0 +1,11 @@
+"HS13 model"
+function hs13(args...; kwargs...)
+  nlp = Model()
+  @variable(nlp, x[i = 1:2] ≥ 0, start = -2)
+
+  @NLobjective(nlp, Min, (x[1] - 2)^2 + x[2]^2)
+
+  @NLconstraint(nlp, (1 - x[1])^3 ≥ x[2])
+
+  return nlp
+end