html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/issues/2004#issuecomment-460881018,https://api.github.com/repos/pydata/xarray/issues/2004,460881018,MDEyOklzc3VlQ29tbWVudDQ2MDg4MTAxOA==,1217238,2019-02-06T02:32:46Z,2019-02-06T02:32:46Z,MEMBER,The performance difference here does indeed to have been fixed with netCDF-C 4.6.2 (but see also https://github.com/pydata/xarray/issues/2747),"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,307318224
https://github.com/pydata/xarray/issues/2004#issuecomment-375067743,https://api.github.com/repos/pydata/xarray/issues/2004,375067743,MDEyOklzc3VlQ29tbWVudDM3NTA2Nzc0Mw==,1217238,2018-03-21T19:29:51Z,2018-03-21T19:29:51Z,MEMBER,"H5py is doing all the hard work for this in h5netcdf.
On Wed, Mar 21, 2018 at 11:51 AM Benjamin Root <notifications@github.com>
wrote:

> Ah, nevermind, I see that our examples only had one greater-than-one stride
>
> —
> You are receiving this because you commented.
> Reply to this email directly, view it on GitHub
> <https://github.com/pydata/xarray/issues/2004#issuecomment-375056363>, or mute
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> .
>
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,307318224
https://github.com/pydata/xarray/issues/2004#issuecomment-375020977,https://api.github.com/repos/pydata/xarray/issues/2004,375020977,MDEyOklzc3VlQ29tbWVudDM3NTAyMDk3Nw==,1217238,2018-03-21T17:08:15Z,2018-03-21T17:08:15Z,MEMBER,"The culprit appears to be netCDF4-python and/or netCDF-C:
```
f = netCDF4.Dataset('test.nc')

%time f['__xarray_dataarray_variable__'][:, ::10]
# CPU times: user 313 ms, sys: 1.23 s, total: 1.54 s
```

When I try doing the same operation with h5netcdf, it runs very quickly:
```python
reopened = xr.open_dataarray('test.nc', engine='h5netcdf')

%time reopened[::1, ::10].compute()
# CPU times: user 6.11 ms, sys: 3.63 ms, total: 9.74 ms
```","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,307318224
https://github.com/pydata/xarray/issues/2004#issuecomment-375010010,https://api.github.com/repos/pydata/xarray/issues/2004,375010010,MDEyOklzc3VlQ29tbWVudDM3NTAxMDAxMA==,1217238,2018-03-21T16:38:59Z,2018-03-21T16:38:59Z,MEMBER,"Here's a simpler case that gets at the essence of the problem:
```python
import xarray as xr
import numpy as np

source = xr.DataArray(np.zeros((100, 12000)), dims=['time', 'x'])
source.to_netcdf('test.nc', format='NETCDF4')
reopened = xr.open_dataarray('test.nc')

%time reopened[::1, ::1].compute()
# CPU times: user 1.35 ms, sys: 6.77 ms, total: 8.12 ms

%time reopened[::1, ::10].compute()
# CPU times: user 371 ms, sys: 1.33 s, total: 1.7 s
```","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,307318224