Exception when getting the index on the CPU backend

[JamesWrigley]

When running this slightly minified code from the quickstart guide:

import KernelAbstractions as KA

KA.@kernel function mul2_kernel(A)
    I = KA.@index(Global, Linear)
end
    
dev = KA.CPU()
A = ones(1024, 1024)
ev = mul2_kernel(dev, 64)(A, ndrange=size(A))
KA.synchronize(dev)
all(A .== 2.0)

I get this exception (only on the CPU backend, the CUDA backend works):

TaskFailedException

    nested task error: MethodError: no method matching __index_Global_Linear(::KernelAbstractions.CompilerMetadata{KernelAbstractions.NDIteration.DynamicSize, KernelAbstractions.NDIteration.NoDynamicCheck, CartesianIndex{2}, CartesianIndices{2, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, KernelAbstractions.NDIteration.NDRange{2, KernelAbstractions.NDIteration.DynamicSize, KernelAbstractions.NDIteration.StaticSize{(64, 1)}, CartesianIndices{2, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, Nothing}})
    The function `__index_Global_Linear` exists, but no method is defined for this combination of argument types.
    
    Closest candidates are:
      __index_Global_Linear(::Any, ::CartesianIndex)
       @ KernelAbstractions ~/.julia/packages/KernelAbstractions/491pi/src/cpu.jl:163
    
    Stacktrace:
     [1] macro expansion
       @ ./In[85]:3 [inlined]
     [2] cpu_mul2_kernel
       @ ~/.julia/packages/KernelAbstractions/491pi/src/macros.jl:291 [inlined]
     [3] (::var"#cpu_mul2_kernel#9")(__ctx__::KernelAbstractions.CompilerMetadata{KernelAbstractions.NDIteration.DynamicSize, KernelAbstractions.NDIteration.NoDynamicCheck, CartesianIndex{2}, CartesianIndices{2, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, KernelAbstractions.NDIteration.NDRange{2, KernelAbstractions.NDIteration.DynamicSize, KernelAbstractions.NDIteration.StaticSize{(64, 1)}, CartesianIndices{2, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, Nothing}}, A::Matrix{Float64})
       @ Main ./none:0
     [4] __thread_run(tid::Int64, len::Int64, rem::Int64, obj::KernelAbstractions.Kernel{CPU, KernelAbstractions.NDIteration.StaticSize{(64,)}, KernelAbstractions.NDIteration.DynamicSize, var"#cpu_mul2_kernel#9"}, ndrange::Tuple{Int64, Int64}, iterspace::KernelAbstractions.NDIteration.NDRange{2, KernelAbstractions.NDIteration.DynamicSize, KernelAbstractions.NDIteration.StaticSize{(64, 1)}, CartesianIndices{2, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, Nothing}, args::Tuple{Matrix{Float64}}, dynamic::KernelAbstractions.NDIteration.NoDynamicCheck)
       @ KernelAbstractions ~/.julia/packages/KernelAbstractions/491pi/src/cpu.jl:144
     [5] (::KernelAbstractions.var"#20#23"{KernelAbstractions.Kernel{CPU, KernelAbstractions.NDIteration.StaticSize{(64,)}, KernelAbstractions.NDIteration.DynamicSize, var"#cpu_mul2_kernel#9"}, Tuple{Int64, Int64}, KernelAbstractions.NDIteration.NDRange{2, KernelAbstractions.NDIteration.DynamicSize, KernelAbstractions.NDIteration.StaticSize{(64, 1)}, CartesianIndices{2, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, Nothing}, Tuple{Matrix{Float64}}, KernelAbstractions.NDIteration.NoDynamicCheck, Int64})()
       @ KernelAbstractions ~/.julia/packages/KernelAbstractions/491pi/src/cpu.jl:119

...and 39 more exceptions.


Stacktrace:
 [1] sync_end(c::Channel{Any})
   @ Base ./task.jl:466
 [2] macro expansion
   @ ./task.jl:499 [inlined]
 [3] __run(obj::KernelAbstractions.Kernel{CPU, KernelAbstractions.NDIteration.StaticSize{(64,)}, KernelAbstractions.NDIteration.DynamicSize, var"#cpu_mul2_kernel#9"}, ndrange::Tuple{Int64, Int64}, iterspace::KernelAbstractions.NDIteration.NDRange{2, KernelAbstractions.NDIteration.DynamicSize, KernelAbstractions.NDIteration.StaticSize{(64, 1)}, CartesianIndices{2, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, Nothing}, args::Tuple{Matrix{Float64}}, dynamic::KernelAbstractions.NDIteration.NoDynamicCheck, static_threads::Bool)
   @ KernelAbstractions ~/.julia/packages/KernelAbstractions/491pi/src/cpu.jl:118
 [4] (::KernelAbstractions.Kernel{CPU, KernelAbstractions.NDIteration.StaticSize{(64,)}, KernelAbstractions.NDIteration.DynamicSize, var"#cpu_mul2_kernel#9"})(args::Matrix{Float64}; ndrange::Tuple{Int64, Int64}, workgroupsize::Nothing)
   @ KernelAbstractions ~/.julia/packages/KernelAbstractions/491pi/src/cpu.jl:46
 [5] top-level scope
   @ In[85]:9

These are the versions I'm running it with:

% julia --project
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.11.1 (2024-10-16)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

(james) pkg> st
Status `Project.toml`
  [824d6782] Bonito v3.2.2
  [052768ef] CUDA v5.5.2
  [f68482b8] Cthulhu v2.15.2
  [8bb1440f] DelimitedFiles v1.9.1
  [7a1cc6ca] FFTW v1.8.0
  [63c18a36] KernelAbstractions v0.9.28
  [2fda8390] LsqFit v0.15.0
  [67456a42] OhMyThreads v0.7.0
  [6099a3de] PythonCall v0.9.23
  [276b4fcb] WGLMakie v0.10.14

[vchuravy]

Huh that's a fun one...

[AntoineBut]

I've encountered the same issue, has anyone found a quick fix to get around the problem?

It doesn't matter if it is inneficient since it only show up on theCPU backend, but it currently prevents me from testing my package in the CI.

[JamesWrigley]

Alas, no. My quick fix is not use CPUs 😎

[AntoineBut]

Great news, will email GitHub to kindly ask they add a few GPU to their runners 🚀🚀

[JamesWrigley]

Actually this is fixed on master, so I'll close it. @vchuravy, any chance of getting a new release with the fix?

[vchuravy]

Master will need some more work to stabilize, it's a breaking release

[JamesWrigley]

Roger that 👍 Out of curiosity, what more work would be necessary? I might be able to find some time for it in the next few weeks.

(not that I know much about KA 😅 )