# Copyto! does not work for subarray when scalar get index is disallowed?

**URL:** https://discourse.julialang.org/t/copyto-does-not-work-for-subarray-when-scalar-get-index-is-disallowed/30044
**Category:** GPU
**Tags:** question
**Created:** [October 18, 2019, 8:37am UTC](https://discourse.julialang.org/t/copyto-does-not-work-for-subarray-when-scalar-get-index-is-disallowed/30044 "2019-10-18T08:37:52Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![ww1g11](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ww1g11/32/14205_2.png) [@ww1g11](https://discourse.julialang.org/u/ww1g11)
#### Post date: [October 18, 2019, 8:37am UTC](https://discourse.julialang.org/t/copyto-does-not-work-for-subarray-when-scalar-get-index-is-disallowed/30044/1 "2019-10-18T08:37:52Z")

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I have a large Array in CPU and want to copy back the GPU data to it. Here is a demo:

```julia
using CuArrays
CuArrays.allowscalar(false)
N = 100
u_c = rand(N, 2);
u_d = CuArrays.CuArray(ones(N));
u_v = view(u_c, :, 1);
copyto!(u_d, u_v) #works
println(Array(u_d)-u_c[:, 1])
copyto!(u_v, u_d) #does not works

```

Any help?

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<div class="post-metadata">

### Author: ![maleadt](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/maleadt/32/10097_2.png) [@maleadt](https://discourse.julialang.org/u/maleadt)
#### Post date: [October 18, 2019, 9:34am UTC](https://discourse.julialang.org/t/copyto-does-not-work-for-subarray-when-scalar-get-index-is-disallowed/30044/2 "2019-10-18T09:34:07Z")

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That should probably work, please file an issue.  
As a workaround, you can do `@allowscalar copyto!(...)` to temporarily allow scalar indexing.