Compile time error

[pengtu]

I am getting a compile time error with the following short program:

#################
#GPU parallel
using PyCall, Printf
using oneAPI
cv2 = pyimport("cv2")

function gpu_parallel_paint!(pixels, t, n)
x = get_global_id(0) - 1
y = get_global_id(1) - 1
c = -0.8f0 + cos(t) * 0.2f0im
z = (y/n - 1 + (x/n - 0.5f0)im) * 2.0f0
iterations = 0
while sqrt(abs2(z)) < 20 && iterations < 50
z = z*z + c
iterations += 1
end
@inbounds pixels[x][y] = 1.0f0 - iterations * 0.02f0
return nothing
end

frames = 1000
n=320
pixels=oneAPI.fill(0.0f0, n, 2*n)

ti = 0.0f0
for i = 1:frames
t = i0.03f0
global ti += @Elapsed @oneapi items=(n, 2n) gpu_parallel_paint!(pixels, t, n)
cv2.imshow("Julia Set", pixels)
cv2.waitKey(1)
end
fps = Int(floor(frames/ti))
println("FPS: ", fps)
cv2.destroyAllWindows()

################

Detailed error message says the kernel function returns a value of 'Union{}' even though I put "return nothing" in the kernel. I am new to Julia language, so it could be a mistake on my part.

Thanks,
Peng.

---

ERROR: LoadError: GPU compilation of kernel gpu_parallel_paint!(oneDeviceArray{Float32,2,1}, Float32, Int64) failed
KernelError: kernel returns a value of type Union{}

Make sure your kernel function ends in return, return nothing or nothing.
If the returned value is of type Union{}, your Julia code probably throws an exception.
Inspect the code with @device_code_warntype for more details.

Stacktrace:
[1] check_method(::GPUCompiler.CompilerJob) at /home/peng/.julia/packages/GPUCompiler/ze8Ok/src/validation.jl:18
[2] macro expansion at /home/peng/.julia/packages/TimerOutputs/dVnaw/src/TimerOutput.jl:206 [inlined]
[3] codegen(::Symbol, ::GPUCompiler.CompilerJob; libraries::Bool, deferred_codegen::Bool, optimize::Bool, strip::Bool, validate::Bool, only_entry::Bool) at /home/peng/.julia/packages/GPUCompiler/ze8Ok/src/driver.jl:63
[4] compile(::Symbol, ::GPUCompiler.CompilerJob; libraries::Bool, deferred_codegen::Bool, optimize::Bool, strip::Bool, validate::Bool, only_entry::Bool) at /home/peng/.julia/packages/GPUCompiler/ze8Ok/src/driver.jl:39
[5] compile at /home/peng/.julia/packages/GPUCompiler/ze8Ok/src/driver.jl:35 [inlined]
[6] #zefunction_compile#42 at /home/peng/.julia/packages/oneAPI/Hn0Ia/src/compiler/execution.jl:123 [inlined]
[7] zefunction_compile(::GPUCompiler.FunctionSpec{typeof(gpu_parallel_paint!),Tuple{oneDeviceArray{Float32,2,1},Float32,Int64}}) at /home/peng/.julia/packages/oneAPI/Hn0Ia/src/compiler/execution.jl:120
[8] check_cache(::Dict{UInt64,Any}, ::Any, ::Any, ::GPUCompiler.FunctionSpec{typeof(gpu_parallel_paint!),Tuple{oneDeviceArray{Float32,2,1},Float32,Int64}}, ::UInt64; kwargs::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}) at /home/peng/.julia/packages/GPUCompiler/ze8Ok/src/cache.jl:40
[9] gpu_parallel_paint! at /home/peng/workspace/sycl-coding/Julia-Set/JuliaLang/fractal_gpu.jl:7 [inlined]
[10] cached_compilation(::Dict{UInt64,Any}, ::typeof(oneAPI.zefunction_compile), ::typeof(oneAPI.zefunction_link), ::GPUCompiler.FunctionSpec{typeof(gpu_parallel_paint!),Tuple{oneDeviceArray{Float32,2,1},Float32,Int64}}; kwargs::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}) at /home/peng/.julia/packages/GPUCompiler/ze8Ok/src/cache.jl:0
[11] cached_compilation(::Dict{UInt64,Any}, ::Function, ::Function, ::GPUCompiler.FunctionSpec{typeof(gpu_parallel_paint!),Tuple{oneDeviceArray{Float32,2,1},Float32,Int64}}) at /home/peng/.julia/packages/GPUCompiler/ze8Ok/src/cache.jl:65
[12] zefunction(::Function, ::Type{T} where T; name::Nothing, kwargs::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}) at /home/peng/.julia/packages/oneAPI/Hn0Ia/src/compiler/execution.jl:113
[13] zefunction(::Function, ::Type{T} where T) at /home/peng/.julia/packages/oneAPI/Hn0Ia/src/compiler/execution.jl:111
[14] macro expansion at /home/peng/.julia/packages/oneAPI/Hn0Ia/src/compiler/execution.jl:34 [inlined]
[15] macro expansion at ./timing.jl:233 [inlined]
[16] top-level scope at /home/peng/workspace/sycl-coding/Julia-Set/JuliaLang/fractal_gpu.jl:27
[17] include(::Function, ::Module, ::String) at ./Base.jl:380
[18] include(::Module, ::String) at ./Base.jl:368
[19] exec_options(::Base.JLOptions) at ./client.jl:296
[20] _start() at ./client.jl:506

[pengtu]

My error: should use 'pixels[x,y] = ...' for multi-dimensional array subscript. Thank you for the email reply.