Added F# function for Broyden method with Jacobian step size and a unit test for that.

src/FSharp/FindRoots.fs

@@ -70,6 +70,11 @@ module FindRoots =
         | true, root -> Some root
         | false, _ -> None
 
+    let broydenWithJacobianStep jacobianStepSize maxIterations accuracy guess (f:float[]->float[]) =
+        match Broyden.TryFindRootWithJacobianStep(tobcl f, guess, accuracy, maxIterations, jacobianStepSize) with
+        | true, root -> Some root
+        | false, _ -> None
+
     // simple usage
 
     let ofFunction lowerBound upperBound (f:float->float) =

src/FSharpUnitTests/FindRootsTests.fs

@@ -59,6 +59,11 @@ module FindRootsTests =
             | Some x -> should (equalWithin 1e-1) [|0.9638680512795; 346.16369814640|]
             | None ->   failwith "The element in array is not equal.") |> ignore
 
+    [<Test>]
+    let ``Bryoden with Jacobian step size should find both roots of (x - 3) * (x - 4)``() =
+        f |> (fun g (x:float[]) -> [|g x.[0]|]) |> FindRoots.broydenWithJacobianStep 1e-6 100 1e-14 [|1.0;|] |> shouldEqual (Some [|3.0|])
+        f |> (fun g (x:float[]) -> [|g x.[0]|]) |> FindRoots.broydenWithJacobianStep 1e-6 100 1e-14 [|9.0;|] |> shouldEqual (Some [|4.0|])
+
     [<Test>]
     let ``Simple method should find both roots of (x - 3) * (x - 4)``() =
         f |> FindRoots.ofFunction -5.0 3.5 |> Option.get |> should (equalWithin 1e-8) 3.0