金属着色语言 - (控制台)输出？

Question

我可以使用控制台输出调试我的金属着色语言代码(如print在Swift中)吗？

如果有,怎么样？

如果不是,有没有其他方法从我的.metal文件输出变量？(也许通过使用commandEncoder-buffer将数据从.metal文件传递到我的.swift文件？)

我没有成功尝试通过commandEncoder传递对Int变量(在我的.swift文件中)的引用到我的.metal文件.在.metal文件中,我为int变量赋值,但是如果我在swift文件中打印Int,则指定的值不存在.

.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;
...
}

控制台输出始终是 myMetalOutput: 0

Answer 1

如果有人需要,这是一个有效的解决方案:

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;

}