add _device attribute to PRNGKeyArray so that computation follows key placement

unrelated: remove some redundant hasattr + try / except AttributeError

jax/_src/numpy/ndarray.py

@@ -31,8 +31,7 @@ class ArrayMeta(abc.ABCMeta):
     # that isinstance(x, ndarray) might return true but
     # issubclass(type(x), ndarray) might return false for an array tracer.
     try:
-      return (hasattr(instance, "aval") and
-              isinstance(instance.aval, core.UnshapedArray))
+      return isinstance(instance.aval, core.UnshapedArray)
     except AttributeError:
       super().__instancecheck__(instance)
 

jax/_src/prng.py

@@ -15,6 +15,7 @@
 
 import abc
 from functools import partial
+import operator as op
 from typing import Any, Callable, Hashable, Iterator, NamedTuple, Sequence
 
 import numpy as np
@@ -114,8 +115,7 @@ class PRNGKeyArrayMeta(abc.ABCMeta):
 
   def __instancecheck__(self, instance):
     try:
-      return (hasattr(instance, 'aval') and
-              isinstance(instance.aval, core.ShapedArray) and
+      return (isinstance(instance.aval, core.ShapedArray) and
               type(instance.aval.dtype) is KeyTy)
     except AttributeError:
       super().__instancecheck__(instance)
@@ -169,6 +169,10 @@ class PRNGKeyArray(metaclass=PRNGKeyArrayMeta):
   def dtype(self):
     return KeyTy(self.impl)
 
+  _device = property(op.attrgetter('_base_array._device'))
+  _committed = property(op.attrgetter('_base_array._committed'))
+  sharding = property(op.attrgetter('_base_array.sharding'))
+
   def _is_scalar(self):
     base_ndim = len(self.impl.key_shape)
     return self._base_array.ndim == base_ndim

tests/multi_device_test.py

@@ -150,6 +150,12 @@ class MultiDeviceTest(jtu.JaxTestCase):
                                                 jax.device_put(x_uncommitted, devices[3])),
                                     devices[4])
 
+  def test_computation_follows_data_prng(self):
+    _, device, *_ = self.get_devices()
+    rng = jax.device_put(jax.random.PRNGKey(0), device)
+    val = jax.random.normal(rng, ())
+    self.assert_committed_to_device(val, device)
+
   def test_primitive_compilation_cache(self):
     devices = self.get_devices()