random-polyhedron generation

docs/src/lib/representations.md

@@ -436,6 +436,7 @@ The following methods are specific for polytopes.
 The following methods are specific for `HPolyhedron`.
 
 ```@docs
+rand(::Type{HPolyhedron})
 vertices_list(::HPolyhedron{Real})
 singleton_list(::HPolyhedron{N}) where {N<:Real}
 ```

src/HPolyhedron.jl

@@ -1,6 +1,7 @@
 using MathProgBase, GLPKMathProgInterface
 
 import Base: isempty,
+             rand,
              convert
 
 export HPolyhedron,
@@ -199,6 +200,48 @@ function ∈(x::AbstractVector{N}, P::HPoly{N})::Bool where {N<:Real}
     return true
 end
 
+"""
+    rand(::Type{HPolyhedron}; [N]::Type{<:Real}=Float64, [dim]::Int=2,
+         [rng]::AbstractRNG=GLOBAL_RNG, [seed]::Union{Int, Nothing}=nothing
+        )::HPolyhedron{N}
+
+Create a polyhedron.
+
+### Input
+
+- `HPolyhedron` -- type for dispatch
+- `N`           -- (optional, default: `Float64`) numeric type
+- `dim`         -- (optional, default: 2) dimension (is ignored)
+- `rng`         -- (optional, default: `GLOBAL_RNG`) random number generator
+- `seed`        -- (optional, default: `nothing`) seed for reseeding
+
+### Output
+
+A polyhedron.
+
+### Algorithm
+
+We first create a random polytope and then randomly remove some of the
+constraints.
+"""
+function rand(::Type{HPolyhedron};
+              N::Type{<:Real}=Float64,
+              dim::Int=2,
+              rng::AbstractRNG=GLOBAL_RNG,
+              seed::Union{Int, Nothing}=nothing
+             )::HPolyhedron{N}
+    rng = reseed(rng, seed)
+    P = rand(HPolytope; N=N, dim=dim, rng=rng)
+    constraints_P = constraints_list(P)
+    constraints_Q = Vector{LinearConstraint{N}}()
+    for i in 1:length(constraints_P)
+        if rand(Bool)
+            push!(constraints_Q, constraints_P[i])
+        end
+    end
+    return HPolyhedron(constraints_Q)
+end
+
 
 # ===========================================
 # HPolyhedron and HPolytope's shared methods

test/unit_Polyhedron.jl

@@ -1,9 +1,8 @@
 global test_suite_polyhedra
 
 for N in [Float64, Rational{Int}, Float32]
-    # -----
-    # H-rep
-    # -----
+    # random polyhedron
+    rand(HPolyhedron)
 
     # constructor from matrix and vector
     A = [N(1) N(2); N(-1) N(1)]
@@ -71,9 +70,6 @@ unconstrained_HPolyhedron = HPolyhedron()
 # Polyhedra tests that only work with Float64
 if test_suite_polyhedra
     for N in [Float64]
-        # -----
-        # H-rep
-        # -----
         # support function/vector
         d = N[1, 0]
         p_unbounded = HPolyhedron([LinearConstraint(N[-1, 0], N(0))])