# How to use/initialize Zygote.Buffer

**URL:** <https://discourse.julialang.org/t/how-to-use-initialize-zygote-buffer/87653>\
**Category:** Machine Learning\
**Tags:** zygote\
**Created:** [September 22, 2022, 2:38pm UTC](https://discourse.julialang.org/t/how-to-use-initialize-zygote-buffer/87653 "2022-09-22T14:38:52Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![LeN3rd](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/len3rd/32/34329_2.png) [@LeN3rd](https://discourse.julialang.org/u/LeN3rd)\
**Post date:** [September 22, 2022, 2:38pm UTC](https://discourse.julialang.org/t/how-to-use-initialize-zygote-buffer/87653/1 "2022-09-22T14:38:52Z")

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This is probably a common question, but when i use Zygote.Buffer i cannot assign values by doing buffer .= old\_data  
It throws the following:

```julia
ERROR: MethodError: no method matching ndims(::Type{Zygote.Buffer{Float64, Matrix{Float64}}})
Closest candidates are:
  ndims(::CUDA.CUSPARSE.CuSparseMatrix) at ~/.julia/packages/CUDA/DfvRa/lib/cusparse/array.jl:225
  ndims(::AbstractFFTs.Plan) at ~/.julia/packages/AbstractFFTs/Wg2Yf/src/definitions.jl:15
  ndims(::ArrayInterfaceCore.ArrayIndex{N}) where N at ~/.julia/packages/ArrayInterfaceCore/7kMjZ/src/ArrayInterfaceCore.jl:578

```

The relevant lines are:

```julia
    image_a = zeros(sensor.image_size)
    image = Zygote.Buffer(image_a, sensor.image_size[1], sensor.image_size[2])
    image .= image_a

```

When i remove the last line, it runs smoothly (at least without gradient), but obviously the image is uninitialized.

Does somebody have an idea what goes wrong here?

Edit:  
This is especially weird, since when i try to show ndims(image) it shows “2” and works as expected

[052768ef] CUDA v3.12.0  
[31c24e10] Distributions v0.25.67  
[5789e2e9] FileIO v1.15.0  
[587475ba] Flux v0.13.5  
[82e4d734] ImageIO v0.6.6  
[6218d12a] ImageMagick v1.2.2  
[a98d9a8b] Interpolations v0.14.5  
[e88e6eb3] Zygote v0.6.44  
[37e2e46d] LinearAlgebra  
[9a3f8284] Random

Julia version 1.7.3

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<div class="post-metadata">

**Author:** ![LeN3rd](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/len3rd/32/34329_2.png) [@LeN3rd](https://discourse.julialang.org/u/LeN3rd)\
**Post date:** [September 23, 2022, 1:40pm UTC](https://discourse.julialang.org/t/how-to-use-initialize-zygote-buffer/87653/2 "2022-09-23T13:40:23Z")

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Update:  
I solved the issue by putting two loops around the Buffer and manually assigning zero to each cell. This is a workaround, but seems to work fine so far.

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<div class="post-metadata">

**Author:** ![ToucheSir](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/touchesir/32/14411_2.png) [@ToucheSir](https://discourse.julialang.org/u/ToucheSir)\
**Post date:** [September 25, 2022, 12:09am UTC](https://discourse.julialang.org/t/how-to-use-initialize-zygote-buffer/87653/3 "2022-09-25T00:09:31Z")

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`Zygote.Buffer` doesn’t support in-place broadcast (`.=`), but you can do `image[:] = image_a` or `copyto!(image, image_a)`. Both will be much, much faster than setting individual elements in a loop.

However, this particular example doesn’t appear to need any of the aforementioned options? Creating a `Buffer` using `Buffer(image_a, false)` or `bufferfrom(image_a)` (both are equivalent) does everything in one step.

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<div class="post-metadata">

**Author:** ![LeN3rd](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/len3rd/32/34329_2.png) [@LeN3rd](https://discourse.julialang.org/u/LeN3rd)\
**Post date:** [September 27, 2022, 2:52pm UTC](https://discourse.julialang.org/t/how-to-use-initialize-zygote-buffer/87653/4 "2022-09-27T14:52:10Z")

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bufferfrom is probably the function need. Thanks for the reply.