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/1995#issuecomment-842556731,https://api.github.com/repos/pydata/xarray/issues/1995,842556731,MDEyOklzc3VlQ29tbWVudDg0MjU1NjczMQ==,35968931,2021-05-17T18:59:18Z,2021-05-17T18:59:18Z,MEMBER,"Has this not been solved by the argument `allow_rechunk`?

@crusaderky isn't this effectively what you were trying to achieve?

```python
import xarray as xr

def mulsum(a, b):
    acc = 0
    for i in range(a.size):
        acc += a[i] * b[i]
    return acc

a = xr.DataArray(data=[1, 2, 3], dims=['x']).chunk({""x"": 1})

b = xr.DataArray(data=[4, 5, 6], dims=['x']).chunk({""x"": 1})

c = xr.apply_ufunc(
    mulsum, a, b,
    input_core_dims=[['x'], ['x']],
    dask='parallelized', output_dtypes=[float],
    dask_gufunc_kwargs={'allow_rechunk': True})

print(c.compute())
```
returns
```
<xarray.DataArray ()>
array(32)
```

I think this has only been possible since the implementation of `xarray.apply_ufunc` was switched from `dask.array.blockwise` to `dask.array.apply_gufunc` in #4060.

If this is actually doing what I think it's doing then we should document this possibility!","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,305757822