Animated plot and CUDA computations with Makie

Specific Domains GPU
, , ,
1

Hello everyone ,
I’m learning GPU programming with Julia and I want to generate a procedurally animated picture inside a window with CUDA , for instance I’m porting the GPU Ripple example from Chapter 5 “Cuda by example” book.
I managed to make it work with Makie but rendering doesn’t look performing really well and even worse I have to transfer the resulting array from GPU to CPU and then update the image.
Is there a better way to do that with Makie or any other library in Julia ? I tried to look into GLFW, GLMakie etc but I had difficulty to understand how those libraries work.

module GPU_RIPPLE

using CUDA
using Makie
using AbstractPlotting
using Colors

const DIM = 1024
const PI = 3.1415926535897932

function kernel(image, ticks)
    # map from threadIdx/blockIdx to pixel position
    x = threadIdx().x + (blockIdx().x - 1) * blockDim().x
    y = threadIdx().y + (blockIdx().y - 1) * blockDim().y
    offset = x + (y-1) * blockDim().x * gridDim().x

    # calculate value at the position
    fx = x - DIM/2
    fy = y - DIM/2
    d = CUDA.sqrt(fx * fx + fy * fy)
    grey = (128.0 + 127.0 * CUDA.cos(d/10.0 - ticks/7.0) / (d/10.0 + 1.0))/255
    image[offset] = grey
    return nothing
end

function main()

    imoutput = zeros(RGB{Float32}, DIM, DIM)
    
    img_node = Node(imoutput)

    num_threads = 16
    num_blocks = ceil(Int, DIM/num_threads)
    blocks = (num_blocks, num_blocks)
    threads = (num_threads, num_threads)

    scene = Scene(background_color=:black)
    scene = image!(img_node, show_axis=false)
    display(scene)

    ticks = 1
    @async while isopen(scene)
        d_imoutput = CuArray(imoutput)
        CUDA.@sync begin
            @cuda blocks=blocks threads=threads kernel(d_imoutput, ticks)
        end
        img_node[] = Array(d_imoutput)
        ticks +=1
        sleep(1/300)
    end
    
end

end
2

There’s no reason to allocate imoutput for every iteration. It’s also performing a copy, where you should just construct a empty CuArray. But ultimately there should be some integration between the plotting library and CUDA.jl so that the array can be used directly, and that is currently not implemented.

3

Thank you very much for your answer @maleadt