ios - Metal 着色语言 - (控制台)输出？

Question

我可以使用控制台输出(如 Swift 中的 print)调试我的 Metal 着色语言代码吗？

如果是，怎么办？

如果没有，是否还有其他方法可以从我的 .metal 文件中输出变量？ (也许通过使用 commandEncoder-buffer 将数据从 .metal 文件传递​​到我的 .swift 文件？)

我试图通过 commandEncoder 将对 Int 变量(在我的 .swift 文件中)的引用传递到我的 .metal 文件，但没有成功。在 .metal 文件中，我为 int 变量赋值，但如果我在我的 swift 文件中打印 Int，则赋值不存在。

.swift 文件:

...
var myMetalOutput: Int = 0
...
let printBuffer = device.newBufferWithBytes(&myMetalOutput, length: sizeof(Int), options: MTLResourceOptions.CPUCacheModeDefaultCache)
commandEncoder.setBuffer(printBuffer, offset: 0, atIndex: 8)
...
commandBuffer.commit()
drawable.present()
print("myMetalOutput: \(myMetalOutput)")
...

. Metal 文件:

...
kernel void shader(..., device int &printBuffer [[8]], ...) {
...
printBuffer = 123;
...
}

控制台输出总是myMetalOutput: 0

Answer 1

这是一个可行的解决方案，以备不时之需:

let device = MTLCreateSystemDefaultDevice()!
let commandQueue = device.newCommandQueue()
let defaultLibrary = device.newDefaultLibrary()!
let commandBuffer = commandQueue.commandBuffer()
let computeCommandEncoder = commandBuffer.computeCommandEncoder()

let program = defaultLibrary.newFunctionWithName("shader")

do
{
    let computePipelineFilter = try device.newComputePipelineStateWithFunction(program!)
    computeCommandEncoder.setComputePipelineState(computePipelineFilter)
    var resultdata = [Int](count: 1, repeatedValue: 0)
    let outVectorBuffer = device.newBufferWithBytes(&resultdata, length: sizeofValue(1), options: MTLResourceOptions.CPUCacheModeDefaultCache)
    computeCommandEncoder.setBuffer(outVectorBuffer, offset: 0, atIndex: 0)


    let threadsPerGroup = MTLSize(width:1,height:1,depth:1)
    let numThreadgroups = MTLSize(width:1, height:1, depth:1)
    computeCommandEncoder.dispatchThreadgroups(numThreadgroups, threadsPerThreadgroup: threadsPerGroup)


    computeCommandEncoder.endEncoding()

    commandBuffer.addCompletedHandler {commandBuffer in
        let data = NSData(bytes: outVectorBuffer.contents(), length: sizeof(NSInteger))
        var out: NSInteger = 0
        data.getBytes(&out, length: sizeof(NSInteger))
        print("data: \(out)")
    }

    commandBuffer.commit()

}
catch
{
    fatalError("newComputePipelineStateWithFunction failed ")
}

着色器:

kernel void shader(device int &printBuffer [[buffer(0)]], uint id [[ thread_position_in_grid ]]) {

    printBuffer = 123;

}