ios - 将数字添加到数组值时,由于执行期间出错,命令缓冲区的 Swift Metal Shader 执行被中止
问题描述
我正在尝试一些非常简单的算法,使用金属 GPU 加速来计算数组中的一些值。在某些情况下,着色器会引发错误,我将解释。错误:由于执行过程中的错误,命令缓冲区的执行被中止。忽略(用于导致先前/过多的 GPU 错误)(IOAF 代码 4)
着色器仅在将值添加到数组索引处的现有值时才会引发此错误。例子:
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);
}}}}
而如果你改变
pixelDistance[pixelIndex] = float(pixelIndex); 和
pixelDistance[pixelIndex] += float(pixelIndex);
它会抛出一个错误。
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())!
解决方案
我有这个问题很长时间了,程序间歇性地崩溃了。事实证明,我正在访问内核中尚未由缓冲区分配的内存。在内核中,我正在执行一个 for 循环 0..<5(即为每个线程输出 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并且没有错误,除了“由于执行期间出现错误而中止命令缓冲区的执行。导致 GPU 挂起错误(IOAF 代码 3)”被抛出。
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