issue_comments

+1

On Tue, Jun 2, 2020 at 11:44 AM Joe Hamman notifications@github.com wrote:

Things seem to have died down here. I suggest we merge this as is. As a reminder, the map_blocks function is still marked as an experimental feature so I'm not too concerned about breaking things in the wild. Better to get some early feedback and iterate on the design.

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Things seem to have died down here. I suggest we merge this as is. As a reminder, the map_blocks function is still marked as an experimental feature so I'm not too concerned about breaking things in the wild. Better to get some early feedback and iterate on the design.

Hello @dcherian! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers:

Comment last updated at 2020-05-29 17:44:28 UTC

This is ready for review.

I've minimized the diff. Once this is merged, I'll do some refactoring.

@dcherian - can you resolve conflicts here?

I fixed that on the template branch. After a rebase, this example works with assert_equal

I've started testing this out and have run into one problem. Here's a simple example that uses template and Dask backed DataArrays in args

```python ds = xr.tutorial.load_dataset('air_temperature')

def func(X, y): ''' a simple reduction (assume the output can't be inferred automatically) ''' return X.sum('time') + y.min('time')

ds = ds.chunk({'lat': 10, 'lon': 10}) X = ds['air'] y = ds['air'] **2 template = X.sum('time')

expected = func(X, y) actual = xr.map_blocks(func, X, args=[y], template=template) xr.testing.assert_identical(actual, expected) ```

This raises:

```python-traceback

KeyError Traceback (most recent call last) <ipython-input-9-5491345c8970> in <module> 5 6 expected = func(X, y) ----> 7 actual = xr.map_blocks(func, X, args=[y], template=template) 8 xr.testing.assert_identical(actual, expected)

/srv/conda/envs/notebook/lib/python3.7/site-packages/xarray/core/parallel.py in map_blocks(func, obj, args, kwargs, template) 424 # even if length of dimension is changed by the applied function 425 expected["shapes"] = { --> 426 k: output_chunks[k][v] for k, v in input_chunk_index.items() 427 } 428 expected["data_vars"] = set(template.data_vars.keys()) # type: ignore

/srv/conda/envs/notebook/lib/python3.7/site-packages/xarray/core/parallel.py in <dictcomp>(.0) 424 # even if length of dimension is changed by the applied function 425 expected["shapes"] = { --> 426 k: output_chunks[k][v] for k, v in input_chunk_index.items() 427 } 428 expected["data_vars"] = set(template.data_vars.keys()) # type: ignore

KeyError: 'time' ```