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/pull/4060#issuecomment-634776667,https://api.github.com/repos/pydata/xarray/issues/4060,634776667,MDEyOklzc3VlQ29tbWVudDYzNDc3NjY2Nw==,1217238,2020-05-27T16:18:24Z,2020-05-27T16:18:24Z,MEMBER,"> * un-equal chunking along non-core dimensions
> 
> The second is not so trivial. I see three possibilities (1) just error, (2) try `dask.array.apply_gufunc` if that fails issue a warning and use the old `apply_blockwise` (3) figure out ourselves if non-core dimensions (called loop dimensions in dask) are not-equally chunked, issue a warning and re-chunk them ourselves. Maybe @shoyer and @dcherian can weight in here.

I am pretty confident that existing behavior of `xarray.apply_ufunc` with un-equal chunks along non-core dimensions is entirely broken. I am OK with just erroring for now.","{""total_count"": 3, ""+1"": 2, ""-1"": 0, ""laugh"": 1, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,618081836
https://github.com/pydata/xarray/pull/4060#issuecomment-634774468,https://api.github.com/repos/pydata/xarray/issues/4060,634774468,MDEyOklzc3VlQ29tbWVudDYzNDc3NDQ2OA==,1217238,2020-05-27T16:14:33Z,2020-05-27T16:14:33Z,MEMBER,"Looking at the internals of `dask.array.apply_gufunc`, it looks like it passes on `**kwargs` to `blockwise`. `blockwise` gets called twice, first with only `**kwargs` and then with both `meta` and `**kwargs`:
https://github.com/dask/dask/blob/77628f2d5248cc61cc366cac3e400b6df5c654c1/dask/array/gufunc.py#L422
https://github.com/dask/dask/blob/77628f2d5248cc61cc366cac3e400b6df5c654c1/dask/array/gufunc.py#L439

So it seems we can actually still pass on a `meta` argument explicitly, at least in the first case.

Here's my suggestion for moving forwarding:

- If `meta` was explicitly set (`meta is not None`), pass it into `apply_gufunc` in `**kwargs`
- Otherwise, omit `meta`.","{""total_count"": 1, ""+1"": 1, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,618081836
https://github.com/pydata/xarray/pull/4060#issuecomment-631702113,https://api.github.com/repos/pydata/xarray/issues/4060,631702113,MDEyOklzc3VlQ29tbWVudDYzMTcwMjExMw==,1217238,2020-05-20T20:16:09Z,2020-05-20T20:16:09Z,MEMBER,"> > Maybe this is too defensive/surprising, and could be relaxed.
> 
> You would remove the `daks=""forbidden""` branch and not the `dask=""parallelized""`?
> 
> For the functions that don't handle dask arrays gracefully, `dask=""parallelized""` would be the better option?

This is probably another good motivation: defaulting to `dask='forbidden'` forces users to make an explicit choice about whether or not use `dask='parallelized'`.

The problem is that we don't have any way to detect ahead of time whether the applied function already supports dask arrays (e.g., if it is built-up out of functions from dask.array). If it does, we don't want to set `dask='parallelized'` but rather let the function handle dask arrays itself.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,618081836
https://github.com/pydata/xarray/pull/4060#issuecomment-631689889,https://api.github.com/repos/pydata/xarray/issues/4060,631689889,MDEyOklzc3VlQ29tbWVudDYzMTY4OTg4OQ==,1217238,2020-05-20T19:50:23Z,2020-05-20T19:50:23Z,MEMBER,"The original motivation for requiring `dask='allowed'` is that I was concerned that users would put a function that coerces its arguments into NumPy arrays into `apply_ufunc` (e.g., like many functions from SciPy), which could have surprisingly bad performance when called on dask arrays due to automatic coercion.

Maybe this is too defensive/surprising, and could be relaxed. We don't really have any guard-rails like this elsewhere in xarray.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,618081836
https://github.com/pydata/xarray/pull/4060#issuecomment-629369850,https://api.github.com/repos/pydata/xarray/issues/4060,629369850,MDEyOklzc3VlQ29tbWVudDYyOTM2OTg1MA==,1217238,2020-05-15T16:56:04Z,2020-05-15T16:56:04Z,MEMBER,"> > * Would it be possible to replace the call to `dask.array.blockwise` (for one output variable) with `dask.array.apply_gufunc`? Do you know why `blockwise` is used further below and not `dask.array.apply_gufunc`? I assume it's due to historical reasons but I am not sure.
> 
> AFAIK, `apply_gufunc` wasn't available at the time these functions were introduced. Good chance, that `apply_gufunc` can be used for handling single output dask too.

Exactly. It would be nice remove the use of `blockwise` entirely in favor of `apply_gufunc`.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,618081836