Add support for max_version, dl_device, copy kwargs in __dlpack__

Author: Micky774

jax/_src/array.py

@@ -404,11 +404,25 @@ def __array__(self, dtype=None, context=None, copy=None):
  kwds = {} if copy is None else {'copy': copy}
  return np.asarray(self._value, dtype=dtype, **kwds)
 
- def __dlpack__(self, *, stream: int | Any | None = None):
- if len(self._arrays) != 1:
- raise BufferError("__dlpack__ only supported for unsharded arrays.")
+ def __dlpack__(self, *, stream: int | Any | None = None,
+ max_version: tuple[int, int] | None = None,
+ dl_device: tuple[enum.Enum, int] | None = None,
+ copy: bool | None = None):
  from jax._src.dlpack import to_dlpack # pylint: disable=g-import-not-at-top
- return to_dlpack(self, stream=stream)
+
+ device_set = self.sharding.device_set
+ if len(device_set) > 1:
+ raise BufferError(
+ "to_dlpack can only pack a dlpack tensor from an array on a singular "
+ f"device, but an array with a Sharding over {len(device_set)} devices "
+ "was provided."
+ )
+ device, = device_set
+ return to_dlpack(self, stream=stream,
+ max_version=max_version,
+ src_device=device,
+ dl_device=dl_device, # type: ignore
+ copy=copy)
 
  def __dlpack_device__(self) -> tuple[enum.Enum, int]:
  if len(self._arrays) != 1:

jax/_src/dlpack.py

@@ -21,10 +21,14 @@
 from jax import numpy as jnp
 from jax._src import array
 from jax._src import xla_bridge
+from jax._src.lax.lax import _array_copy
 from jax._src.lib import xla_client
 from jax._src.lib import xla_extension_version
 from jax._src.typing import Array
+from jax._src.api import device_put
 
+DLPACK_VERSION = (0, 8)
+MIN_DLPACK_VERSION = (0, 5)
 
 # A set of dtypes that dlpack supports.
 # Note: Make sure to use a "type", not a dtype instance, when looking up this set
@@ -48,9 +52,34 @@ class DLDeviceType(enum.IntEnum):
  kDLCUDA = 2
  kDLROCM = 10
 
+def _to_dlpack(x: Array, stream: int | Any | None,
+ src_device: xla_client.Device | None = None,
+ device: xla_client.Device | None = None,
+ copy: bool | None = None):
+
+ if src_device is None:
+ src_device, = x.devices()
+ if device and (src_device is None or device != src_device):
+ if copy is not None and not copy:
+ raise ValueError(
+ f"Specified {device=} which requires a copy since the source device "
+ f"is {repr(src_device)}, however copy=False. Set copy=True or "
+ "copy=None to perform the requested operation."
+ )
+ else:
+ arr = device_put(x, device)
+ else:
+ arr = _array_copy(x) if copy else x
+ return xla_client._xla.buffer_to_dlpack_managed_tensor(
+ arr.addressable_data(0), stream=stream
+ )
 
 def to_dlpack(x: Array, take_ownership: bool = False,
- stream: int | Any | None = None):
+ stream: int | Any | None = None,
+ src_device: xla_client.Device | None = None,
+ dl_device: tuple[DLDeviceType, int] | None = None,
+ max_version: tuple[int, int] | None = None,
+ copy : bool | None = None):
  """Returns a DLPack tensor that encapsulates a :class:`~jax.Array` ``x``.
 
  Args:
@@ -60,27 +89,97 @@ def to_dlpack(x: Array, take_ownership: bool = False,
  stream: optional platform-dependent stream to wait on until the buffer is
  ready. This corresponds to the `stream` argument to ``__dlpack__``
  documented in https://dmlc.github.io/dlpack/latest/python_spec.html.
+ src_device: either a CPU or GPU :class:`~jax.Device`.
+ dl_device: a tuple of ``(dl_device_type, local_hardware_id)`` in DLPack
+ format e.g. as produced by ``__dlpack_device__``.
+ max_version: the maximum DLPack version that the consumer (i.e. caller of
+ ``__dlpack__``) supports in the form of a 2-tuple of ``(major, minor)``.
+ This function is not guaranteed to return a capsule of version
+ ``max_version``.
+ copy: a boolean indicating whether or not to copy the input. If
+ ``copy=True`` then the function must always copy. When
+ ``copy=False`` then the function must never copy, and must raise an error
+ when a copy is deemed necessary. If ``copy=None`` then the function must
+ avoid a copy if possible but may copy if needed.
 
  Returns:
- A dlpack PyCapsule object.
+ A DLPack PyCapsule object.
 
  Note:
- While JAX arrays are always immutable, dlpack buffers cannot be marked as
- immutable, and it is possible for processes external to JAX to mutate them
- in-place. If a dlpack buffer derived from a JAX array is mutated, it may
- lead to undefined behavior when using the associated JAX array.
+ While JAX arrays are always immutable, ``DLPackManagedTensor`` buffers
+ cannot be marked as immutable, and it is possible for processes external
+ to JAX to mutate them in-place. If a DLPack buffer derived from a JAX array
+ is mutated, it may lead to undefined behavior when using the associated JAX
+ array. When JAX eventually supports ``DLManagedTensorVersioned``
+ (DLPack 1.0), it will be possible to specify that a buffer is read-only.
  """
  if not isinstance(x, array.ArrayImpl):
  raise TypeError("Argument to to_dlpack must be a jax.Array, "
  f"got {type(x)}")
- assert len(x.devices()) == 1
  if take_ownership:
  warnings.warn(
  "take_ownership in to_dlpack is deprecated and it is a no-op."
  )
- return xla_client._xla.buffer_to_dlpack_managed_tensor(
- x.addressable_data(0), stream=stream
- ) # type: ignore
+
+ device = None
+ dl_device_type, local_hardware_id = dl_device if dl_device else (None, None)
+ if dl_device_type:
+ try:
+ dl_device_platform = {
+ DLDeviceType.kDLCPU: "cpu",
+ DLDeviceType.kDLCUDA: "cuda",
+ DLDeviceType.kDLROCM: "rocm",
+ }[dl_device_type]
+ backend = xla_bridge.get_backend(dl_device_platform)
+ device = backend.device_from_local_hardware_id(local_hardware_id)
+ except TypeError:
+ # https://data-apis.org/array-api/latest/API_specification/generated/array_api.array.__dlpack__.html
+ # recommends using BufferError.
+ raise BufferError(
+ "The device specification passed to to_dlpack contains an unsupported "
+ f"device type (DLDeviceType: {dl_device_type})")
+
+ # TODO(micky774): Deprecate default usage of DLPackManagedTensor when XLA
+ # supports DLManagedTensorVersioned (DLPack version 1.0) and repurpose the
+ # current _to_dlpack as a legacy path for (0,5) <= max_version < (1,0)
+ if max_version is None:
+ # Backwards compatible default
+ return _to_dlpack(
+ x, stream=stream,
+ src_device=src_device,
+ device=device,
+ copy=copy
+ )
+ else:
+ if max_version >= DLPACK_VERSION:
+ # Latest
+ return _to_dlpack(
+ x, stream=stream,
+ src_device=src_device,
+ device=device,
+ copy=copy
+ )
+ if max_version[0] == DLPACK_VERSION[0]:
+ # ABI compatible
+ return _to_dlpack(
+ x, stream=stream,
+ src_device=src_device,
+ device=device,
+ copy=copy
+ )
+ elif max_version >= MIN_DLPACK_VERSION:
+ # Oldest supported
+ return _to_dlpack(
+ x, stream=stream,
+ src_device=src_device,
+ device=device,
+ copy=copy
+ )
+ else:
+ raise BufferError(
+ f"JAX does not support any version below {MIN_DLPACK_VERSION} but "
+ f"version ({max_version}) was requested."
+ )
 
 
 def from_dlpack(external_array):
@@ -110,12 +209,12 @@ def from_dlpack(external_array):
  DLDeviceType.kDLCUDA: "cuda",
  DLDeviceType.kDLROCM: "rocm",
  }[dl_device_type]
- except TypeError:
+ except TypeError as err:
  # https://dmlc.github.io/dlpack/latest/python_spec.html recommends using
  # TypeError.
- raise TypeError(
+ raise BufferError(
  "Array passed to from_dlpack is on unsupported device type "
- f"(DLDeviceType: {dl_device_type}, array: {external_array}")
+ f"(DLDeviceType: {dl_device_type}, array: {external_array}") from err
 
  backend = xla_bridge.get_backend(device_platform)
  device = backend.device_from_local_hardware_id(device_id)

tests/array_interoperability_test.py

@@ -74,24 +74,49 @@ def setUp(self):
  shape=all_shapes,
  dtype=dlpack_dtypes,
  gpu=[False, True],
+ copy=[False, True, None]
  )
- def testJaxRoundTrip(self, shape, dtype, gpu):
+ def testJaxRoundTrip(self, shape, dtype, gpu, copy):
  if xb.using_pjrt_c_api():
  self.skipTest("DLPack support is incomplete in the PJRT C API") # TODO(skyewm)
  rng = jtu.rand_default(self.rng())
  np = rng(shape, dtype)
- if gpu and jtu.test_device_matches(["cpu"]):
- raise unittest.SkipTest("Skipping GPU test case on CPU")
+ if gpu and not jtu.test_device_matches(["gpu"]):
+ raise unittest.SkipTest("Skipping GPU test case on CPU/TPU")
+
+ def _check_copy(x, y, expect_copy):
+ is_copy = x.unsafe_buffer_pointer() != y.unsafe_buffer_pointer()
+ assert is_copy == expect_copy
+
+ # Check if the source device is preserved
+ x = jax.device_put(np, jax.devices("cpu")[0])
  device = jax.devices("gpu" if gpu else "cpu")[0]
- x = jax.device_put(np, device)
- dlpack = jax.dlpack.to_dlpack(x)
- y = jax.dlpack.from_dlpack(dlpack)
- self.assertEqual(y.devices(), {device})
- self.assertAllClose(np.astype(x.dtype), y)
+ y = jax.device_put(x, device)
+ dlpack = jax.dlpack.to_dlpack(y, copy=copy)
+ z = jax.dlpack.from_dlpack(dlpack)
 
+ self.assertEqual(z.devices(), {device})
+ self.assertAllClose(np.astype(x.dtype), z)
  self.assertRaisesRegex(RuntimeError,
- "DLPack tensor may be consumed at most once",
- lambda: jax.dlpack.from_dlpack(dlpack))
+ "DLPack tensor may be consumed at most once",
+ lambda: jax.dlpack.from_dlpack(dlpack))
+
+ if shape in nonempty_array_shapes:
+ _check_copy(y, z, bool(copy))
+
+ # Check if the destination device can be specified
+ dl_device = y.__dlpack_device__()
+ make_dlpack = lambda: x.__dlpack__(dl_device=dl_device, copy=copy)
+ if gpu and copy == False:
+ self.assertRaisesRegex(ValueError, "copy=False", make_dlpack)
+ return
+
+ z = jax.dlpack.from_dlpack(make_dlpack())
+ self.assertEqual(z.devices(), {device})
+ self.assertAllClose(np.astype(x.dtype), z)
+
+ if shape in nonempty_array_shapes:
+ _check_copy(x, z, bool(copy) or gpu)
 
  @jtu.sample_product(
  shape=all_shapes,