Add __array_namespace_info__ and corresponding utilities

jax/experimental/array_api/__init__.py

@@ -204,6 +204,7 @@
 )
 
 from jax.experimental.array_api._utility_functions import (
+    __array_namespace_info__ as __array_namespace_info__,
     all as all,
     any as any,
 )

jax/experimental/array_api/_utility_functions.py

@@ -12,8 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import jax
+from __future__ import annotations
 
+import jax
+from typing import Tuple
+from jax._src.sharding import Sharding
+from jax._src.lib import xla_client as xc
+from jax._src import dtypes as _dtypes, config
 
 def all(x, /, *, axis=None, keepdims=False):
   """Tests whether all input array elements evaluate to True along a specified axis."""
@@ -23,3 +28,66 @@ def all(x, /, *, axis=None, keepdims=False):
 def any(x, /, *, axis=None, keepdims=False):
   """Tests whether any input array element evaluates to True along a specified axis."""
   return jax.numpy.any(x, axis=axis, keepdims=keepdims)
+
+class __array_namespace_info__:
+
+  def __init__(self):
+    self._capabilities = {
+      "boolean indexing": True,
+      "data-dependent shapes": False,
+    }
+
+
+  def _build_dtype_dict(self):
+    array_api_types = {
+      "bool", "int8", "int16",
+      "int32", "uint8", "uint16",
+      "uint32", "float32", "complex64"
+    }
+    if config.enable_x64.value:
+      array_api_types |= {"int64", "uint64", "float64", "complex128"}
+    return {category: {t.name: t for t in types if t.name in array_api_types}
+            for category, types in _dtypes._dtype_kinds.items()}
+
+  def default_device(self):
+    # By default JAX arrays are uncommitted (device=None), meaning that
+    # JAX is free to choose the most efficient device placement.
+    return None
+
+  def devices(self):
+    return jax.devices()
+
+  def capabilities(self):
+    return self._capabilities
+
+  def default_dtypes(self, *, device: xc.Device | Sharding | None = None):
+    # Array API supported dtypes are device-independent in JAX
+    del device
+    default_dtypes = {
+      "real floating": "f",
+      "complex floating": "c",
+      "integral": "i",
+      "indexing": "i",
+    }
+    return {
+      dtype_name: _dtypes.canonicalize_dtype(
+        _dtypes._default_types.get(kind)
+      ) for dtype_name, kind in default_dtypes.items()
+    }
+
+  def dtypes(
+      self, *,
+      device: xc.Device | Sharding | None = None,
+      kind: str | Tuple[str, ...] | None = None):
+    # Array API supported dtypes are device-independent in JAX
+    del device
+    data_types = self._build_dtype_dict()
+    if kind is None:
+      out_dict = data_types["numeric"] | data_types["bool"]
+    elif isinstance(kind, tuple):
+      out_dict = {}
+      for _kind in kind:
+        out_dict |= data_types[_kind]
+    else:
+      out_dict = data_types[kind]
+    return out_dict

tests/BUILD

@@ -54,6 +54,7 @@ py_test(
     deps = [
         "//jax",
         "//jax:experimental_array_api",
+        "//jax:test_util",
     ] + py_deps("absl/testing"),
 )
 

tests/array_api_test.py

@@ -21,9 +21,11 @@
 
 from types import ModuleType
 
-from absl.testing import absltest
+from absl.testing import absltest, parameterized
 import jax
-from jax import config
+import jax.numpy as jnp
+from jax._src import config, test_util as jtu
+from jax._src.dtypes import _default_types, canonicalize_dtype
 from jax.experimental import array_api
 
 config.parse_flags_with_absl()
@@ -232,6 +234,86 @@ def test_array_namespace_method(self):
     self.assertIsInstance(x, jax.Array)
     self.assertIs(x.__array_namespace__(), array_api)
 
+class ArrayAPIInspectionUtilsTest(jtu.JaxTestCase):
+
+  info = array_api.__array_namespace_info__()
+
+  def setUp(self):
+    super().setUp()
+    self._boolean = self.build_dtype_dict(["bool"])
+    self._signed = self.build_dtype_dict(["int8", "int16", "int32"])
+    self._unsigned = self.build_dtype_dict(["uint8", "uint16", "uint32"])
+    self._floating = self.build_dtype_dict(["float32"])
+    self._complex = self.build_dtype_dict(["complex64"])
+    if config.enable_x64.value:
+      self._signed["int64"] = jnp.dtype("int64")
+      self._unsigned["uint64"] = jnp.dtype("uint64")
+      self._floating["float64"] = jnp.dtype("float64")
+      self._complex["complex128"] = jnp.dtype("complex128")
+    self._integral = self._signed | self._unsigned
+    self._numeric = (
+      self._signed | self._unsigned | self._floating | self._complex
+    )
+  def build_dtype_dict(self, dtypes):
+    out = {}
+    for name in dtypes:
+        out[name] = jnp.dtype(name)
+    return out
+
+  def test_capabilities_info(self):
+    capabilities = self.info.capabilities()
+    assert capabilities["boolean indexing"]
+    assert not capabilities["data-dependent shapes"]
+
+  def test_default_device_info(self):
+    assert self.info.default_device() is None
+
+  def test_devices_info(self):
+    assert self.info.devices() == jax.devices()
+
+  def test_default_dtypes_info(self):
+    _default_dtypes = {
+      "real floating": "f",
+      "complex floating": "c",
+      "integral": "i",
+      "indexing": "i",
+    }
+    target_dict = {
+      dtype_name: canonicalize_dtype(
+        _default_types.get(kind)
+      ) for dtype_name, kind in _default_dtypes.items()
+    }
+    assert self.info.default_dtypes() == target_dict
+
+  @parameterized.parameters(
+    "bool", "signed integer", "real floating",
+    "complex floating", "integral", "numeric", None,
+    (("real floating", "complex floating"),),
+    (("integral", "signed integer"),),
+    (("integral", "bool"),),
+  )
+  def test_dtypes_info(self, kind):
+
+    info_dict = self.info.dtypes(kind=kind)
+    control = {
+      "bool":self._boolean,
+      "signed integer":self._signed,
+      "unsigned integer":self._unsigned,
+      "real floating":self._floating,
+      "complex floating":self._complex,
+      "integral": self._integral,
+      "numeric": self._numeric
+    }
+    target_dict = {}
+    if kind is None:
+      target_dict = control["numeric"] | self._boolean
+    elif isinstance(kind, tuple):
+      target_dict = {}
+      for _kind in kind:
+        target_dict |= control[_kind]
+    else:
+      target_dict = control[kind]
+    assert info_dict == target_dict
 
 if __name__ == '__main__':
   absltest.main()