# Can't install package CuArrays
**URL:** https://discourse.julialang.org/t/cant-install-package-cuarrays/71368
**Category:** General Usage
**Tags:** question, package, cuda
**Created:** [November 12, 2021, 8:39am UTC](https://discourse.julialang.org/t/cant-install-package-cuarrays/71368 "2021-11-12T08:39:04Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Niceno](https://discourse.julialang.org/u/Niceno)
#### Post date: [November 12, 2021, 8:39am UTC](https://discourse.julialang.org/t/cant-install-package-cuarrays/71368/1 "2021-11-12T08:39:04Z")
Dear all,
I am trying to learn CUDA from the book “CUDA by Example” by Sanders and Kandrot. The book is based on C, so I am translating their examples to Julia. I got stuck at their example 3.2.3, which you can see here: [https://github.com/yottaawesome/cuda-by-example/blob/master/src/chapter03/simple\_kernel\_params.cu](https://github.com/yottaawesome/cuda-by-example/blob/master/src/chapter03/simple_kernel_params.cu)
I wrote the Julia counterpart as this:
```julia
using CUDA
function add!(a :: Int64,
b :: Int64,
c :: CuDeviceVector{Int64})
c[1] = a + b
return nothing
end
function main()
c = zeros(Int64, 1); # variable on the host
dev_c = CuArray{Int64}(undef, 1) # variable on the device
@cuda threads=1 blocks=1 add!(2, 7, dev_c) # call GPU kernel function add!
c = Array(dev_c) # copy from device's to host
println("2 + 7 = ", c[1]) # print the result
CUDA.unsafe_free!(dev_c) # free the memory on the device
end
```
This works as expected, but I don’t like the line: `c = Array(dev_c)`, I find it somehow non-intuitive. Instead, I tried to use `CyArrays.copyto!()`, but I get the error saying `CuArrays` were not defined. Command `using CuArrays` tells me that `CuArrays` were not installed, and suggest me to import the package the usual Julian way. However, importing the package results in the following error:
```julia
ERROR: Unsatisfiable requirements detected for package CUDAapi [3895d2a7]:
CUDAapi [3895d2a7] log:
├─possible versions are: 0.5.0-4.0.0 or uninstalled
├─restricted by compatibility requirements with CuArrays [3a865a2d] to versions: 0.5.0-4.0.0
│ └─CuArrays [3a865a2d] log:
│ ├─possible versions are: 0.2.1-2.2.2 or uninstalled
│ └─restricted to versions * by an explicit requirement, leaving only versions 0.2.1-2.2.2
└─restricted by julia compatibility requirements to versions: uninstalled — no versions left
```
So I wonder: are CuArrays deprecated? How can one use command: `CyArrays.copyto!()`, unless it is deprecated too?
_Cheers_
---
### Author:  [@nilshg](https://discourse.julialang.org/u/nilshg)
#### Post date: [November 12, 2021, 8:54am UTC](https://discourse.julialang.org/t/cant-install-package-cuarrays/71368/2 "2021-11-12T08:54:26Z")
Which Julia version are you using?
---
### Author:  [@Niceno](https://discourse.julialang.org/u/Niceno)
#### Post date: [November 12, 2021, 8:55am UTC](https://discourse.julialang.org/t/cant-install-package-cuarrays/71368/3 "2021-11-12T08:55:40Z")
1.6.3
---
### Author:  [@nilshg](https://discourse.julialang.org/u/nilshg)
#### Post date: [November 12, 2021, 8:57am UTC](https://discourse.julialang.org/t/cant-install-package-cuarrays/71368/4 "2021-11-12T08:57:54Z")
That won’t work, see here:
[https://github.com/JuliaRegistries/General/blob/master/C/CUDAapi/Compat.toml](https://github.com/JuliaRegistries/General/blob/master/C/CUDAapi/Compat.toml)
Apparently this is the “old CUDA stack” which shouldn’t be used on Julia \>1.6. So this is probably just a case of an outdated example in the book - if you absolutely want to run it, you’d have to do so on Julia 1.5.4.
---
### Author:  [@Niceno](https://discourse.julialang.org/u/Niceno)
#### Post date: [November 12, 2021, 9:01am UTC](https://discourse.julialang.org/t/cant-install-package-cuarrays/71368/5 "2021-11-12T09:01:27Z")
Thanks!
---
### Author:  [@maleadt](https://discourse.julialang.org/u/maleadt)
#### Post date: [November 15, 2021, 6:31am UTC](https://discourse.julialang.org/t/cant-install-package-cuarrays/71368/6 "2021-11-15T06:31:58Z")
> [@Niceno](#):
>
> This works as expected, but I don’t like the line: `c = Array(dev_c)` , I find it somehow non-intuitive. Instead, I tried to use `CyArrays.copyto!()` , but I get the error saying `CuArrays` were not defined.
Just use `copyto!`, there’s no need for a module prefix. The method you want to call is defined by the CUDA module, no need to use any of the old packages (like CuArrays.jl).