我无法在手机中运行任何金属计算着色器

Question

我正在尝试在iPhone SE上运行我的金属程序

我为threadsPerThreadGroup和threadsPerGrid大小尝试了许多数字，所有这些都给了我这个错误：TLValidateFeatureSupport:3539: failed assertion `Dispatch Threads with Non-Uniform Threadgroup Size is only supported on MTLGPUFamilyApple4 and later.'

这是我的代码

var threadsPerThreadGroup: MTLSize
var threadsPerGrid: MTLSize

computeCommandEncoder.setComputePipelineState(updateShader)

let w = updateShader.threadExecutionWidth

threadsPerThreadGroup = MTLSize(width: w, height: 1, depth: 1)
threadsPerGrid = MTLSize(width: Int(constants.bufferLength), height: 1, depth: 1)

if(frames % 2 == 0) {
    computeCommandEncoder.setBuffer(buffer1, offset: 0, index: 0)
    computeCommandEncoder.setBuffer(buffer2, offset: 0, index: 1)
} else {
    computeCommandEncoder.setBuffer(buffer2, offset: 0, index: 0)
    computeCommandEncoder.setBuffer(buffer1, offset: 0, index: 1)
}

 computeCommandEncoder.setBytes(&constants, length: MemoryLayout<MyConstants>.stride, index: 2)

computeCommandEncoder.dispatchThreads(threadsPerGrid, threadsPerThreadgroup: threadsPerThreadGroup)

frames += 1

我正在使用iOS 13.4和XCode 11.4

threadExecutionWidth的计算结果为32，并且constants.bufferLength为512

Answer 1

Use [dispatchThreads] only if the device supports non-uniform threadgroup sizes.

措词不够清晰。这意味着在A11之前的GPU上，dispatchThreads 不起作用。

如果要使解决方案适用于所有设备，则必须自己计算网格中有多少线程组，并使用dispatchThreadgroups。

如果要在代码中同时使用这两种方法，则可以detect the device's feature set at runtime。