问如何在使用金属API时请求使用集成GPU？

EN

    NSArray<id<MTLDevice>> *devices = MTLCopyAllDevices();

    gpu_ = nil;

    // Low power device is sufficient - try to use it!
    for (id<MTLDevice> device in devices) {
        if (device.isLowPower) {
            gpu_ = device;
            break;
        }
    }

    // below: probably not necessary since there is always 
    // integrated GPU, but doesn't hurt.
    if (gpu_ == nil)
        gpu_ = MTLCreateSystemDefaultDevice();