Update minimum version of dask

[jhamman]

Xarray currently states that it supports dask version 0.9 and later. However, 1) I don't think this is true and my quick test shows that some of our tests fail using dask 0.9, and 2) we have a growing number of tests that are being skipped for older dask versions:

$ grep -irn "dask.__version__" xarray/tests/*py
xarray/tests/__init__.py:90:    if LooseVersion(dask.__version__) < '0.18':
xarray/tests/test_computation.py:755:        if LooseVersion(dask.__version__) < LooseVersion('0.17.3'):
xarray/tests/test_computation.py:841:    if not use_dask or LooseVersion(dask.__version__) > LooseVersion('0.17.4'):
xarray/tests/test_dask.py:211:    @pytest.mark.skipif(LooseVersion(dask.__version__) <= '0.15.4',
xarray/tests/test_dask.py:223:    @pytest.mark.skipif(LooseVersion(dask.__version__) <= '0.15.4',
xarray/tests/test_dask.py:284:    @pytest.mark.skipif(LooseVersion(dask.__version__) <= '0.15.4',
xarray/tests/test_dask.py:296:    @pytest.mark.skipif(LooseVersion(dask.__version__) <= '0.15.4',
xarray/tests/test_dask.py:387:        if LooseVersion(dask.__version__) == LooseVersion('0.15.3'):
xarray/tests/test_dask.py:784:    pytest.mark.skipif(LooseVersion(dask.__version__) <= '0.15.4',
xarray/tests/test_dask.py:802:    pytest.mark.skipif(LooseVersion(dask.__version__) <= '0.15.4',
xarray/tests/test_dask.py:818:@pytest.mark.skipif(LooseVersion(dask.__version__) <= '0.15.4',
xarray/tests/test_variable.py:1664:        if LooseVersion(dask.__version__) <= LooseVersion('0.15.1'):
xarray/tests/test_variable.py:1670:        if LooseVersion(dask.__version__) <= LooseVersion('0.15.1'):

I'd like to see xarray bump the minimum version number of dask to something around 0.15.4 (Oct. 2017) or 0.16 (Nov. 2017).

cc @mrocklin, @pydata/xarray

[fujiisoup]

DataArray.dot() is using dask.einsum, and it only woks with dask >= 0.17.5 (#2089).

Does this requirement sound is too strict? If so, it maybe better to add another pass for older dask.

[jhamman]

We have traditionally allowed for a fairly large lag in version dependencies so I'd guess that 0.17.5 (May 16, 2018) is too recent. That said, I'm in favor of shrinking that window to facilitate faster integration of new features.

[shoyer]

Requiring 0.15.4 seems reasonable to me. There is virtue in supporting a (small) range of versions in dependencies. But clearly 0.9 was too out of date here.

We should probably add a CI test against the oldest version of dask that we support, just to make sure things don't sneak through.

[jhamman]

Can I update my recommendation to 0.16? That is the version that added the new collection interface.

[fujiisoup]

How do we consider the minimum version of optional dependency?
If we say "the minimum version of dask is 0.16", then all our dask related functions should work with dask=0.16?
or do we allow functions that only work with newer version of dask if we raise an appropriate error message?

[shoyer]

The policy I've tried to keep to is keeping everything working with base supported version, but we can add new features that rely on new dask features.

…

On Wed, May 30, 2018 at 8:20 PM Keisuke Fujii ***@***.***> wrote: How do we consider the minimum version of *optional* dependency? If we say "the minimum version of dask is 0.16", then all our dask related functions should work with dask=0.16? or do we allow functions that only work with newer version of dask if we raise an appropriate error message? — You are receiving this because you are on a team that was mentioned. Reply to this email directly, view it on GitHub <#2203 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABKS1uTxKa_GJxvqVj2H2LvL-IYTOCWPks5t32FugaJpZM4UT_GD> .