add conversion from zonotope to sspz (#2991)

* add convertion from zonotope to sspz * update docs * Apply suggestions from code review Co-authored-by: Christian Schilling <[email protected]> * dispatch on AbstractZonotope * update docstring * Update src/convert.jl Co-authored-by: Christian Schilling <[email protected]> Co-authored-by: Marcelo Forets <[email protected]>
JuliaReach · Jul 12, 2022 · bb3b3dd · bb3b3dd
1 parent 8fc8b1c
commit bb3b3dd
Show file tree

Hide file tree

Showing 3 changed files with 30 additions and 0 deletions.
diff --git a/docs/src/lib/conversion.md b/docs/src/lib/conversion.md
@@ -59,4 +59,5 @@ convert(::Type{Zonotope}, ::CartesianProductArray{N, AZ}) where {N, AZ<:Abstract
 convert(::Type{STAR}, ::AbstractPolyhedron{N}) where {N}
 convert(::Type{STAR}, ::Star)
 convert(::Type{Star}, ::AbstractPolyhedron{N}) where {N}
+convert(::Type{SimpleSparsePolynomialZonotope}, ::AbstractZonotope)
 ```
diff --git a/src/convert.jl b/src/convert.jl
@@ -1225,3 +1225,25 @@ function convert(::Type{Hyperplane}, P::HPolyhedron; skip_check::Bool=false)
     c1 = @inbounds first(constraints_list(P))
     return Hyperplane(c1.a, c1.b)
 end
+
+
+"""
+    convert(::Type{SimpleSparsePolynomialZonotope}, Z::Zonotope)
+
+Convert a zonotope to a simple sparse polynomial zonotope.
+
+### Algorithm
+
+This method implements Proposition 3 in [1].
+
+[1] Kochdumper, Althoff. *Sparse polynomial zonotopes - a novel set
+representation for reachability analysis*. 2021
+"""
+function convert(::Type{SimpleSparsePolynomialZonotope}, Z::AbstractZonotope)
+    c = center(Z)
+    G = genmat(Z)
+    n = ngens(Z)
+    E = Matrix(1 * I, n, n)
+
+    return SimpleSparsePolynomialZonotope(c, G, E)
+end
diff --git a/test/Sets/SimpleSparsePolynomialZonotope.jl b/test/Sets/SimpleSparsePolynomialZonotope.jl
@@ -13,6 +13,13 @@ for N in [Float64, Float32, Rational{Int}]
     @test nparams(S) == 2
     @test order(S) == 1 // 1
 
+    for Z in [rand(Zonotope), rand(Hyperrectangle)]
+        ZS = convert(SimpleSparsePolynomialZonotope, Z)
+        @test center(ZS) == center(Z)
+        @test genmat(ZS) == genmat(Z)
+        @test expmat(ZS) == I
+    end
+
     @test overapproximate(S, Zonotope) == Zonotope(N[3., 1], N[1 1;2 1.])
     @test length(overapproximate(S, Zonotope; nsdiv=3)) == 9
     @test length(overapproximate(S, Zonotope; partition=(2, 3))) == 6