mps.swift

func buildGraph(device: MTLDevice) -> MPSNNGraph {
  let inputNode = MPSNNImageNode()
  let node1 = SomeNode1(input: inputNode, weights: ...)
  let node2 = SomeNode2(input: node1.resultImage, weights: ...)
  let node3 = SomeNode3(input: node2.resultImage, weights: ...)
  .....
  return MPSNNGraph(device: device,
                    resultImage: nodeN.resultImage)
}

....

let device = MTLCreateSystemDefaultDevice()
let graph = buildGraph(device: device)
graph.executeAsync(withSourceImages: [inputImage]) { outputImage, error in
  // parse data from outputImage
}