benchmark streaming speed with tar vs zip archives
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I'm closing the PR since we're not going to merge it
2022-03-03T14:55:33Z
https://github.com/huggingface/datasets/pull/3812#issuecomment-1058123634
https://api.github.com/repos/huggingface/datasets/issues/3812
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2022-03-03T14:55:33Z
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# do not merge
## Hypothesis 
packing data into a single zip archive could allow us not to care about splitting data into several tar archives for efficient streaming which is annoying (since data creators usually host the data in a single tar)

## Data

I host it [here](https://huggingface.co/datasets/polinaeterna/benchmark_dataset/)

## I checked three configurations:
1. All data in one zip archive, streaming only those files that exist in split metadata file (we can access them directrly with no need to iterate over full archive), see [this func](https://github.com/huggingface/datasets/compare/master...polinaeterna:benchmark-tar-zip?expand=1#diff-4f5200d4586aec5b2a89fcf34441c5f92156f9e9d408acc7e50666f9a1921ddcR196)
2.  All data in three splits, the standart way to make streaming efficient, see [this func](https://github.com/huggingface/datasets/compare/master...polinaeterna:benchmark-tar-zip?expand=1#diff-4f5200d4586aec5b2a89fcf34441c5f92156f9e9d408acc7e50666f9a1921ddcR174)
3. All data in single tar, iterate over the full archive and take only files existing in split metadata file, see [this func](https://github.com/huggingface/datasets/compare/master...polinaeterna:benchmark-tar-zip?expand=1#diff-4f5200d4586aec5b2a89fcf34441c5f92156f9e9d408acc7e50666f9a1921ddcR150) 

## Results
1. one zip
![image](https://user-images.githubusercontent.com/16348744/156567611-e3652087-7147-4cf0-9047-9cbc00ec71f5.png)
2. three tars
![image](https://user-images.githubusercontent.com/16348744/156567688-2a462107-f83e-4722-8ea3-71a13b56c998.png)
3. one tar
![image](https://user-images.githubusercontent.com/16348744/156567772-1bceb5f7-e7d9-4fa3-b31b-17fec5f9a5a7.png)

didn't check on the full data as it's time consuming but anyway it's pretty obvious that one-zip-way is not a good idea. here it's even worse than full iteration over tar containing all three splits (but that would depend on the case).
