[orx-gradient-descent] convert to MPP

orx-gradient-descent/src/jvmTest/kotlin/TestGradient.kt

@@ -0,0 +1,43 @@
+import org.amshove.kluent.`should be equal to`
+import org.amshove.kluent.`should equal`
+import org.openrndr.extra.gradientdescent.gradient
+import org.spekframework.spek2.Spek
+import org.spekframework.spek2.style.specification.describe
+
+object TestGradient : Spek({
+    describe("a simple 1d function") {
+        fun parabola(x: DoubleArray): Double {
+            return x[0] * x[0]
+        }
+        it("its gradient at x=0 is 0.0") {
+            val g0 = gradient(doubleArrayOf(0.0), ::parabola)
+            g0.size `should equal` 1
+            g0[0] `should be equal to` 0.0
+        }
+        it("its gradient at x=1 is ~2.0") {
+            val g1 = gradient(doubleArrayOf(1.0), ::parabola)
+        }
+        it("its gradient at x=-1 is ~-2.0") {
+            val g1 = gradient(doubleArrayOf(-1.0), ::parabola)
+        }
+    }
+
+    describe("a simple 2d function") {
+        fun parabola(x: DoubleArray): Double {
+            return x[0] * x[0] + x[1] * x[1]
+        }
+
+        it("its gradient at x=0 is 0.0") {
+            val g0 = gradient(doubleArrayOf(0.0, 0.0), ::parabola)
+            g0.size `should equal` 2
+            g0[0] `should be equal to` 0.0
+        }
+
+        it("its gradient at x=1 is ~2.0") {
+            val g1 = gradient(doubleArrayOf(1.0, 1.0), ::parabola)
+        }
+        it("its gradient at x=-1 is ~-2.0") {
+            val g1 = gradient(doubleArrayOf(-1.0, -1.0), ::parabola)
+        }
+    }
+})