determine_backend_multi

uarray.determine_backend_multi(dispatchables, *, domain, only=True, coerce=False, **kwargs)[source]

Set a backend supporting all dispatchables

This is useful for functions that call multimethods without any dispatchable arguments. You can use determine_backend_multi() to ensure the same backend is used everywhere in a block of multimethod calls involving multiple arrays.

Parameters

  • dispatchables (Sequence[Union[uarray.Dispatchable, Any]]) – The dispatchables that must be supported

  • domain (string) – The domain to query for backends and set.

  • coerce (bool) – Whether or not to allow coercion to the backend’s types. Implies only.

  • only (bool) – Whether or not this should be the last backend to try.

  • dispatch_type (Optional[Any]) – The default dispatch type associated with dispatchables, aka “marking”.

See also

determine_backend()

For a single dispatch value

set_backend()

For when you know which backend to set

Notes

Support is determined by the __ua_convert__ protocol. Backends not supporting the type must return NotImplemented from their __ua_convert__ if they don’t support input of that type.

Examples

determine_backend() allows the backend to be set from a single object. determine_backend_multi() allows multiple objects to be checked simultaneously for support in the backend. Suppose we have a BackendAB which supports TypeA and TypeB in the same call, and a BackendBC that doesn’t support TypeA.

>>> with ua.set_backend(ex.BackendAB), ua.set_backend(ex.BackendBC):
...     a, b = ex.TypeA(), ex.TypeB()
...     with ua.determine_backend_multi(
...         [ua.Dispatchable(a, "mark"), ua.Dispatchable(b, "mark")],
...         domain="ua_examples"
...     ):
...         res = ex.creation_multimethod()
...         ex.call_multimethod(res, a, b)
TypeA

This won’t call BackendBC because it doesn’t support TypeA.

We can also use leave out the ua.Dispatchable if we specify the default dispatch_type for the dispatchables argument.

>>> with ua.set_backend(ex.BackendAB), ua.set_backend(ex.BackendBC):
...     a, b = ex.TypeA(), ex.TypeB()
...     with ua.determine_backend_multi(
...         [a, b], dispatch_type="mark", domain="ua_examples"
...     ):
...         res = ex.creation_multimethod()
...         ex.call_multimethod(res, a, b)
TypeA