Merge pull request #31 from JuliaIntervals/gradient

Gradient operator

Author: lbenet

src/IntervalRootFinding.jl

@@ -63,6 +63,15 @@ include("krawczyk.jl")
 include("complex.jl")
 include("branch_and_prune.jl")
 
+
+gradient(f) = X -> ForwardDiff.gradient(f, SVector(X))
+const ∇ = gradient
+
+export ∇
+
+
+
+
 function find_roots{T}(f::Function, a::Interval{T}, method::Function = newton;
                     tolerance = eps(T), debug = false, maxlevel = 30)
 

test/roots.jl

@@ -54,3 +54,9 @@ end
     rts = roots(g, IntervalBox(X, 3))
     @test length(rts) == 4
 end
+
+@testset "Stationary points" begin
+    f(xx) = ( (x, y) = xx; sin(x) * sin(y) )
+    rts = roots(∇(f), IntervalBox(-5..6, 2), Newton, 1e-5)
+    @test length(rts) == 25
+end