MAINT: validate device on numpy and dask

Author: crusaderky

array_api_compat/common/_helpers.py

@@ -595,11 +595,29 @@ def your_function(x, y):
 # backwards compatibility alias
 get_namespace = array_namespace
 
-def _check_device(xp, device):
-    if xp == sys.modules.get('numpy'):
-        if device not in ["cpu", None]:
+
+def _check_device(bare_xp, device):
+    """
+    Validate dummy device on device-less array backends.
+
+    Notes
+    -----
+    This function is also invoked by CuPy, which does have multiple devices
+    if there are multiple GPUs available.
+    However, CuPy multi-device support is currently impossible
+    without using the global device or a context manager:
+
+    https://github.com/data-apis/array-api-compat/pull/293
+    """
+    if bare_xp is sys.modules.get('numpy'):
+        if device not in ("cpu", None):
             raise ValueError(f"Unsupported device for NumPy: {device!r}")
 
+    elif bare_xp is sys.modules.get('dask.array'):
+        if device not in ("cpu", _DASK_DEVICE, None):
+            raise ValueError(f"Unsupported device for Dask: {device!r}")
+
+
 # Placeholder object to represent the dask device
 # when the array backend is not the CPU.
 # (since it is not easy to tell which device a dask array is on)

array_api_compat/dask/array/_aliases.py

@@ -25,7 +25,7 @@
 )
 import dask.array as da
 
-from ...common import _aliases, array_namespace
+from ...common import _aliases, _helpers, array_namespace
 from ...common._typing import (
     Array,
     Device,
@@ -56,6 +56,7 @@ def astype(
     specification for more details.
     """
     # TODO: respect device keyword?
+    _helpers._check_device(da, device)
 
     if not copy and dtype == x.dtype:
         return x
@@ -86,6 +87,7 @@ def arange(
     specification for more details.
     """
     # TODO: respect device keyword?
+    _helpers._check_device(da, device)
 
     args = [start]
     if stop is not None:
@@ -155,6 +157,7 @@ def asarray(
     specification for more details.
     """
     # TODO: respect device keyword?
+    _helpers._check_device(da, device)
 
     if isinstance(obj, da.Array):
         if dtype is not None and dtype != obj.dtype:

array_api_compat/numpy/_aliases.py

@@ -3,7 +3,7 @@
 from typing import Optional, Union
 
 from .._internal import get_xp
-from ..common import _aliases
+from ..common import _aliases, _helpers
 from ..common._typing import NestedSequence, SupportsBufferProtocol
 from ._info import __array_namespace_info__
 from ._typing import Array, Device, DType
@@ -95,8 +95,7 @@ def asarray(
     See the corresponding documentation in the array library and/or the array API
     specification for more details.
     """
-    if device not in ["cpu", None]:
-        raise ValueError(f"Unsupported device for NumPy: {device!r}")
+    _helpers._check_device(np, device)
 
     if hasattr(np, '_CopyMode'):
         if copy is None:
@@ -122,6 +121,7 @@ def astype(
     copy: bool = True,
     device: Optional[Device] = None,
 ) -> Array:
+    _helpers._check_device(np, device)
     return x.astype(dtype=dtype, copy=copy)