Merge pull request #1013 from JuliaReach/mforets/1011

#1011 - Convert to Vector in polyhedron's LP

src/HPolyhedron.jl

@@ -151,8 +151,23 @@ function σ(d::AbstractVector{N}, P::HPoly{N}) where {N<:Real}
     end
 end
 
+@inline function _to_minus_vector(d::SparseVector{N}) where {N}
+    c = zeros(N, length(d))
+    for (ni, i) in enumerate(d.nzind)
+        @inbounds c[i] = -d.nzval[ni]
+    end
+    return c
+end
+
+@inline function _to_minus_vector(d::AbstractVector{N}) where {N}
+    return convert(Vector{N}, -d)
+end
+
 function σ_helper(d::AbstractVector{N}, P::HPoly{N}) where {N<:Real}
-    c = -d
+
+    # let c = -d as a Vector, since GLPK doesn't accept sparse vectors (see #1011)
+    c = _to_minus_vector(d)
+
     (A, b) = tosimplehrep(P)
     if length(b) == 0
         unbounded = true

test/unit_Polytope.jl

@@ -274,3 +274,9 @@ if test_suite_polyhedra
         @test ispermutation(vl, [N[0, 0, 2], N[1, 1, 2]])
     end
 end
+
+# test that one can pass a sparse vector as the direction (see #1011)
+P = HPolytope([HalfSpace([1.0, 0.0], 1.0),
+               HalfSpace([0.0, 1.0], 1.0),
+               HalfSpace([-1.0, -1.0], -1.0)])
+@test an_element(P) ∈ P