Hello there! I tried my best again and here what I got: First If you replace MTLCommandBuffer with MPSCommandBuffer     func encodeTrainingBatch(commandBuffer: MPSCommandBuffer,                              sourceTensorData: MPSGraphTensorData,                              labelsTensorData: MPSGraphTensorData,                              completion: ((Float) -> Void)?) -> MPSGraphTensorData { and call it like this:         let commandBuffer = gCommandQueue.makeCommandBuffer()!         let mpsCommandBuffer = MPSCommandBuffer(commandBuffer: commandBuffer)         var yLabels: MPSNDArray? = nil         let xInput = dataset.getRandomTrainingBatch(device: gDevice, batchSize: batchSize, labels: &yLabels)         _ = classiferGraph.encodeTrainingBatch(commandBuffer: mpsCommandBuffer,                                                sourceTensorData: MPSGraphTensorData(xInput),                                                labelsTensorData: MPSGraphTensorData(yLabels!),                                                completion: updateProgressCubeAndLoss)         mpsCommandBuffer.commitAndContinue() it starts working... But only on iPad version on Mac :D It won't do anything on physical iPhone device (more on this down the line) Second one If you replace graph.encode(to: to graph.runAsync( you no longer need to control commandBuffer and it's also solves the issue Third As I mentioned previously, you can replace MTLCommandBuffer with MPSCommandBuffer it will solve the issue on iPad build running on macOS. BUT it not working on physical iPhone. I mean, it doesn't crash, but descriptor not calling completionHandler. BUT If you add completion handler with addCompletedHandler on commandBuffer, it WILL run! Appendix I don't know why it works the way I explained before, but it seems that for now best way is to use runAsync because it does not need MPSCommandBuffer which cause the bug #1 and it calls completionHandler of MPSGraphExecutionDescriptor in every configuration Hope it will help someone and I hope for Apple developers answers >_>