将数字添加到数组值时，由于执行期间发生错误，命令缓冲区的Swift Metal Shader执行被中止

Question

我正在尝试使用金属GPU加速的一些非常简单的算法来计算数组中的某些值。 在某些情况下，着色器将引发错误。 错误：由于执行期间发生错误，命令缓冲区的执行被中止。 被忽略（导致先前/过度的GPU错误）（IOAF代码4）

仅当将值添加到数组索引处的现有值时，着色器才会引发此错误。 例：

这不会导致错误：

    kernel void shader (device int *wPointsIntensity [[buffer(0)]],
                const device uint *wPointsXCoord [[buffer(1)]],
                const device uint *wPointsYCoord [[buffer(2)]],
                device float *pixelSignalIntensity [[buffer(3)]],
                device float *pixelDistance [[buffer(4)]],
                const device uint& noOfPoints [[ buffer(5) ]],
                const device uint& width [[ buffer(6) ]],
                const device uint& height [[ buffer(7) ]],
                uint id [[ thread_position_in_grid ]]) {

//this does not throw error
for (uint wpIndex = 0; wpIndex < noOfPoints; wpIndex++) {
    for (uint heightIndex = 0; heightIndex < height; heightIndex++) {
        for (uint widthIndex = 0; widthIndex < width; widthIndex++) {

            uint pixelIndex = heightIndex * width + widthIndex;
            pixelDistance[pixelIndex] = float(pixelIndex);
            pixelSignalIntensity[pixelIndex] = float(pixelIndex);
}}}}

如果你改变

pixelDistance [pixelIndex] = float（pixelIndex）; 同

pixelDistance [pixelIndex] + = float（pixelIndex）;

它将引发错误。

这是快速代码：

var wPointsValues = [Int32](repeating:0, count: wPoints.count)
var wPointsXLocations = [Int32](repeating:0, count: wPoints.count)
var wPointsYLocations = [Int32](repeating:0, count: wPoints.count)
        for i in 0..<wPoints.count {
            wPointsValues[i] = Int32(wPoints[i].signalIntensity)
            wPointsXLocations[i] = Int32(wPoints[i].location.x)
            wPointsYLocations[i] = Int32(wPoints[i].location.y)
        }

        var numberOfWPoints:Int32 = Int32(wPoints.count)
        var int32Width = Int32(width)
        var int32Height = Int32(height)

        //output arrays

        let numberOfResults = wPoints.count * Int(width) * Int(height)
        var wPointsSignalIntensity = [Float32](repeating:0.0, count: numberOfResults)
        var wPointsDistance = [Float32](repeating:0.0, count: numberOfResults)


        //local variables
        var signalDensity:[Float32] = [Float32](repeating:0.0, count: numberOfResults)
        var signalDistance:[Float32] = [Float32](repeating:0.0, count: numberOfResults)

            //create input buffers
            let inWPointSignalValues = device.makeBuffer(bytes: wPointsValues, length: (MemoryLayout<Int32>.stride * wPoints.count), options: [])
            let inWPointXCoordBuffer = device.makeBuffer(bytes: wPointsXLocations, length: (MemoryLayout<Int32>.stride * wPoints.count), options: [])
            let inWPointYCoordBuffer = device.makeBuffer(bytes: wPointsYLocations, length: (MemoryLayout<Int32>.stride * wPoints.count), options: [])

            //create putput buffers
            let outPixelSignalIntensityBuffer = device.makeBuffer(bytes: wPointsSignalIntensity, length: (MemoryLayout<Float32>.stride * numberOfResults), options: [])
            let outPixelDistanceBuffer = device.makeBuffer(bytes: wPointsDistance, length: (MemoryLayout<Float32>.stride * numberOfResults), options: [])

            let commandBuffer = (mtlCommmandQueue?.makeCommandBuffer())!
            let computeCommandEncoder = (commandBuffer.makeComputeCommandEncoder())!
            computeCommandEncoder.setComputePipelineState(mtlComputePipelineFilter!)
            //set input buffers
            computeCommandEncoder.setBuffer(inWPointSignalValues, offset: 0, index: 0)
            computeCommandEncoder.setBuffer(inWPointXCoordBuffer, offset: 0, index: 1)
            computeCommandEncoder.setBuffer(inWPointYCoordBuffer, offset: 0, index: 2)

            //set output buffers
            computeCommandEncoder.setBuffer(outPixelSignalIntensityBuffer, offset: 0, index: 3)
            computeCommandEncoder.setBuffer(outPixelDistanceBuffer, offset: 0, index: 4)

            //set constants
            computeCommandEncoder.setBytes(&numberOfWPoints, length: MemoryLayout<Int32>.stride, index: 5)
            computeCommandEncoder.setBytes(&int32Width, length: MemoryLayout<Int32>.stride, index: 6)
            computeCommandEncoder.setBytes(&int32Height, length: MemoryLayout<Int32>.stride, index: 7)


            let threadsPerGroup = MTLSize(width:2,height:2,depth:2)
            let numThreadgroups = MTLSize(width:2, height:2, depth:2)
            computeCommandEncoder.dispatchThreadgroups(numThreadgroups, threadsPerThreadgroup: threadsPerGroup)

            let endBufferAllocation = mach_absolute_time()

            print("time for creating and setting buffert: time: \(Double(endBufferAllocation - start) / Double(NSEC_PER_SEC))")
            computeCommandEncoder.endEncoding()

            commandBuffer.commit()
            commandBuffer.waitUntilCompleted()
            let allComplete = mach_absolute_time()
        self.signalDistance = (outPixelDistanceBuffer?.contents())!
        self.signalDensity = (outPixelSignalIntensityBuffer?.contents())!

Answer 1

我有这个问题很久了，程序间歇性崩溃。 原来，我正在访问内核中尚未由缓冲区分配的内存。 在内核中，我正在执行for循环0 .. <5（即，每个线程输出5个值），但没有将num_threads除以5。

当它没有崩溃时，它给出了正确的答案，没有错误，只抛出了“由于执行过程中的错误导致命令缓冲区的执行中止。导致GPU挂起错误（IOAF代码3）”。