issues: 1171916710

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
1171916710 I_kwDOAMm_X85F2gem 6372 apply_ufunc + dask="parallelized" + no core dimensions should raise a nicer error about core dimensions being absent 2448579 open 0     0 2022-03-17T04:25:37Z 2022-03-17T05:10:16Z   MEMBER      

What happened?

From https://github.com/pydata/xarray/discussions/6370

Calling apply_ufunc(..., dask="parallelized") with no core dimensions and dask input "works" but raises an error on compute (ValueError: axes don't match array from np.transpose).

python xr.apply_ufunc( lambda x: np.mean(x), dt, dask="parallelized" )

What did you expect to happen?

With numpy data the apply_ufunc call does raise an error:

xr.apply_ufunc( lambda x: np.mean(x), dt.compute(), dask="parallelized" )

ValueError: applied function returned data with unexpected number of dimensions. Received 0 dimension(s) but expected 1 dimensions with names: ('x',)

Minimal Complete Verifiable Example

``` python import xarray as xr

dt = xr.Dataset( data_vars=dict( value=(["x"], [1,1,2,2,2,3,3,3,3,3]), ), coords=dict( lon=(["x"], np.linspace(0,1,10)), ), ).chunk(chunks={'x': tuple([2,3,5])}) # three chunks of different size

xr.apply_ufunc( lambda x: np.mean(x), dt, dask="parallelized" ) ```

Relevant log output

No response

Anything else we need to know?

No response

Environment

N/A

 
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