# How to use Dagger.jl's blocks to read a multifile NCDataset?
**URL:** https://discourse.julialang.org/t/how-to-use-dagger-jls-blocks-to-read-a-multifile-ncdataset/24264
**Category:** General Usage
**Created:** [May 16, 2019, 12:50am UTC](https://discourse.julialang.org/t/how-to-use-dagger-jls-blocks-to-read-a-multifile-ncdataset/24264 "2019-05-16T00:50:23Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@aramirezreyes](https://discourse.julialang.org/u/aramirezreyes)
#### Post date: [May 16, 2019, 12:50am UTC](https://discourse.julialang.org/t/how-to-use-dagger-jls-blocks-to-read-a-multifile-ncdataset/24264/1 "2019-05-16T00:50:23Z")
Hi!
I’m trying to load a multifile dataset using NCDatasets, and to speed things up I am trying to use dagger in this way
```nohighlight
include("test/test_catarrays.jl") # this creates some small test files
mfds = Dataset(fnames);
X = Distribute(Blocks(2,3,1), variable(mfds,"var"))
collect(sum(X,dims = 3))
# same results as
sum(variable(mfds,"var")[:,:,:],dims = 3)
```
This is something experimental in NCDatasets and I saw it in [here](https://github.com/Alexander-Barth/NCDatasets.jl/issues/16#issuecomment-439649331) Now, I’ve tried to use it to load my own variables but I don’t really get the meaning of `Blocks` and how should I select that. So far I have only discovered that if I pass `Blocks` a different number of arguments than the dimensions in the array to be read from the file, it throws an error. Other than that I don’t seem to notice how to make it work, sometimes it just stays there forever without completing the task.
Does anyone have any experience using Dagger that can throw a light on this?
---
### Author:  [@jpsamaroo](https://discourse.julialang.org/u/jpsamaroo)
#### Post date: [May 16, 2019, 12:54am UTC](https://discourse.julialang.org/t/how-to-use-dagger-jls-blocks-to-read-a-multifile-ncdataset/24264/2 "2019-05-16T00:54:16Z")
Hey again! Two things:
1. Can you post an MWE so we can easily reproduce what you’re trying to do?: [Please read: make it easier to help you](https://discourse.julialang.org/t/psa-make-it-easier-to-help-you/14757)
2. Your two questions at the end of your post were accidentally included in your code block; you should move them outside the block so it’s obvious that you want people to answer them 😛
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### Author:  [@aramirezreyes](https://discourse.julialang.org/u/aramirezreyes)
#### Post date: [May 16, 2019, 1:01am UTC](https://discourse.julialang.org/t/how-to-use-dagger-jls-blocks-to-read-a-multifile-ncdataset/24264/3 "2019-05-16T01:01:50Z")
I will try to prepare a MWE. Fell free to remove the post and I can create it again with the full info!
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### Author:  [@jpsamaroo](https://discourse.julialang.org/u/jpsamaroo)
#### Post date: [May 16, 2019, 11:08am UTC](https://discourse.julialang.org/t/how-to-use-dagger-jls-blocks-to-read-a-multifile-ncdataset/24264/4 "2019-05-16T11:08:46Z")
No need to delete it, just edit the original post and then reply here so we know that it’s been updated 🙂