Check if CUDA availability changed during init.

src/Flux.jl

@@ -22,15 +22,10 @@ export SGD, Descent, ADAM, Momentum, Nesterov, RMSProp,
 
 using CUDAapi
 if has_cuda()
-  try
-    using CuArrays
-    @eval has_cuarrays() = true
-  catch ex
-    @warn "CUDA is installed, but CuArrays.jl fails to load" exception=(ex,catch_backtrace())
-    @eval has_cuarrays() = false
-  end
+  using CuArrays
+  use_cuda() = true
 else
-  has_cuarrays() = false
+  use_cuda() = false
 end
 
 include("utils.jl")
@@ -47,8 +42,20 @@ include("data/Data.jl")
 
 include("deprecations.jl")
 
-if has_cuarrays()
+if use_cuda()
   include("cuda/cuda.jl")
 end
 
+function __init__()
+  if has_cuda() != use_cuda()
+      cachefile = if VERSION >= v"1.3-"
+          Base.compilecache_path(Base.PkgId(Flux))
+      else
+          abspath(DEPOT_PATH[1], Base.cache_file_entry(Base.PkgId(Flux)))
+      end
+      rm(cachefile)
+      error("Your set-up changed, and Flux.jl needs to be reconfigured. Please load the package again.")
+  end
+end
+
 end # module

src/functor.jl

@@ -73,7 +73,7 @@ end
 
 cpu(m) = fmap(x -> adapt(Array, x), m)
 
-const gpu_adaptor = if has_cuarrays()
+const gpu_adaptor = if use_cuda()
   CuArrays.cu
 else
   identity

src/onehot.jl

@@ -37,7 +37,7 @@ import Adapt: adapt, adapt_structure
 
 adapt_structure(T, xs::OneHotMatrix) = OneHotMatrix(xs.height, adapt(T, xs.data))
 
-if has_cuarrays()
+if use_cuda()
   import .CuArrays: CuArray, cudaconvert
   import Base.Broadcast: BroadcastStyle, ArrayStyle
   BroadcastStyle(::Type{<:OneHotMatrix{<:CuArray}}) = ArrayStyle{CuArray}()