GPU Support
NVIDIA GPU support should work out of the box on systems with CUDA and CUDNN installed. For more details see the CUDA readme.
GPU Usage
Support for array operations on other hardware backends, like GPUs, is provided by external packages like CUDA. Flux is agnostic to array types, so we simply need to move model weights and data to the GPU and Flux will handle it.
For example, we can use CUDA.CuArray
(with the cu
converter) to run our basic example on an NVIDIA GPU.
(Note that you need to have CUDA available to use CUDA.CuArray – please see the CUDA.jl instructions for more details.)
using CUDA
W = cu(rand(2, 5)) # a 2×5 CuArray
b = cu(rand(2))
predict(x) = W*x .+ b
loss(x, y) = sum((predict(x) .- y).^2)
x, y = cu(rand(5)), cu(rand(2)) # Dummy data
loss(x, y) # ~ 3
Note that we convert both the parameters (W
, b
) and the data set (x
, y
) to cuda arrays. Taking derivatives and training works exactly as before.
If you define a structured model, like a Dense
layer or Chain
, you just need to convert the internal parameters. Flux provides fmap
, which allows you to alter all parameters of a model at once.
d = Dense(10, 5, σ)
d = fmap(cu, d)
d.W # CuArray
d(cu(rand(10))) # CuArray output
m = Chain(Dense(10, 5, σ), Dense(5, 2), softmax)
m = fmap(cu, m)
d(cu(rand(10)))
As a convenience, Flux provides the gpu
function to convert models and data to the GPU if one is available. By default, it'll do nothing, but loading CUDA
will cause it to move data to the GPU instead.
julia> using Flux, CUDA
julia> m = Dense(10,5) |> gpu
Dense(10, 5)
julia> x = rand(10) |> gpu
10-element CuArray{Float32,1}:
0.800225
⋮
0.511655
julia> m(x)
5-element CuArray{Float32,1}:
-0.30535
⋮
-0.618002
The analogue cpu
is also available for moving models and data back off of the GPU.
julia> x = rand(10) |> gpu
10-element CuArray{Float32,1}:
0.235164
⋮
0.192538
julia> x |> cpu
10-element Array{Float32,1}:
0.235164
⋮
0.192538