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Add support for copy kwarg in astype to match Array API
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Micky774 committed Apr 19, 2024
1 parent c7517b8 commit 973e921
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6 changes: 6 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -49,6 +49,12 @@ Remember to align the itemized text with the first line of an item within a list
* Scalar arguments to {func}`jax.numpy.nonzero`, {func}`jax.numpy.where`, and
related functions now raise an error, following a similar change in NumPy.

* Bug fixes
* {func}`jax.numpy.astype` will now always return a copy when `copy=True`.
Previously, no copy would be made when the output array would have the same
dtype as the input array. This may result in some increased memory usage.
To prevent copying when possible, set `copy=False`.

## jaxlib 0.4.27

## jax 0.4.26 (April 3, 2024)
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6 changes: 4 additions & 2 deletions jax/_src/numpy/array_methods.py
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Expand Up @@ -31,11 +31,13 @@
import numpy as np
import jax
from jax import lax
from jax.sharding import Sharding
from jax._src import core
from jax._src import dtypes
from jax._src.api_util import _ensure_index_tuple
from jax._src.array import ArrayImpl
from jax._src.lax import lax as lax_internal
from jax._src.lib import xla_client as xc
from jax._src.numpy import lax_numpy
from jax._src.numpy import reductions
from jax._src.numpy import ufuncs
Expand All @@ -55,15 +57,15 @@
# functions, which can themselves handle instances from any of these classes.


def _astype(arr: ArrayLike, dtype: DTypeLike) -> Array:
def _astype(arr: ArrayLike, dtype: DTypeLike, copy: bool = True, device: xc.Device | Sharding | None = None) -> Array:
"""Copy the array and cast to a specified dtype.
This is implemented via :func:`jax.lax.convert_element_type`, which may
have slightly different behavior than :meth:`numpy.ndarray.astype` in
some cases. In particular, the details of float-to-int and int-to-float
casts are implementation dependent.
"""
return lax_numpy.astype(arr, dtype)
return lax_numpy.astype(arr, dtype, copy=copy, device=device)


def _nbytes(arr: ArrayLike) -> int:
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48 changes: 42 additions & 6 deletions jax/_src/numpy/lax_numpy.py
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Expand Up @@ -2272,17 +2272,53 @@ def _convert_to_array_if_dtype_fails(x: ArrayLike) -> ArrayLike:
In particular, the details of float-to-int and int-to-float casts are
implementation dependent.
""")
def astype(x: ArrayLike, dtype: DTypeLike | None, /, *, copy: bool = True) -> Array:
def astype(x: ArrayLike, dtype: DTypeLike | None,
/, *, copy: bool | DeprecatedArg = DeprecatedArg(),
device: xc.Device | Sharding | None = None) -> Array:
util.check_arraylike("astype", x)
x_arr = asarray(x)
del copy # unused in JAX

# TODO(micky774): Deprecated 2024-4-19, remove after deprecation completed.
if isinstance(copy, DeprecatedArg):
warnings.warn(
"The copy keyword of astype was previously ignored but is now "
"implemented. The default of copy=True will lead to the expected "
"behavior of creating a copy, which may potentially lead to extra "
"memory usage. To preserve previous behavior, use copy=False. To "
"suppress this warning, please explicitly set copy.",
DeprecationWarning, stacklevel=2)
copy = False

if dtype is None:
dtype = dtypes.canonicalize_dtype(float_)
dtypes.check_user_dtype_supported(dtype, "astype")
# convert_element_type(complex, bool) has the wrong semantics.
if np.dtype(dtype) == bool and issubdtype(x_arr.dtype, complexfloating):
return (x_arr != _lax_const(x_arr, 0))
return lax.convert_element_type(x_arr, dtype)
if issubdtype(x_arr.dtype, complexfloating):
if dtypes.isdtype(dtype, ("integral", "real floating")):
warnings.warn(
"Casting from complex to real dtypes will soon raise a ValueError. "
"Please first use jnp.real or jnp.imag to take the real/imaginary "
"component of your input.",
DeprecationWarning, stacklevel=2
)
elif np.dtype(dtype) == bool:
# convert_element_type(complex, bool) has the wrong semantics.
x_arr = (x_arr != _lax_const(x_arr, 0))

# We offer a more specific warning than the usual ComplexWarning so we prefer
# to issue our warning.
with warnings.catch_warnings():
warnings.simplefilter("ignore", ComplexWarning)
return _place_array(
lax.convert_element_type(x_arr, dtype),
device=device, copy=copy,
)

def _place_array(x, device=None, copy=None):
# TODO(micky774): Implement in future PRs as we formalize device placement
# semantics
if copy:
return _array_copy(x)
return x


@util.implements(np.asarray, lax_description=_ARRAY_DOC)
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20 changes: 18 additions & 2 deletions jax/experimental/array_api/_data_type_functions.py
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Expand Up @@ -12,13 +12,18 @@
# See the License for the specific language governing permissions and
# limitations under the License.

from __future__ import annotations

import builtins
import functools
from typing import NamedTuple
import jax
import jax.numpy as jnp


from jax._src.lib import xla_client as xc
from jax._src.sharding import Sharding
from jax._src import dtypes as _dtypes
from jax.experimental.array_api._dtypes import (
bool, int8, int16, int32, int64, uint8, uint16, uint32, uint64,
float32, float64, complex64, complex128
Expand Down Expand Up @@ -124,8 +129,19 @@ def _promote_types(t1, t2):
raise ValueError("No promotion path for {t1} & {t2}")


def astype(x, dtype, /, *, copy=True):
return jnp.array(x, dtype=dtype, copy=copy)
def astype(x, dtype, /, *, copy: builtins.bool = True, device: xc.Device | Sharding | None = None):
src_dtype = x.dtype if hasattr(x, "dtype") else _dtypes.dtype(x)
if (
src_dtype is not None
and _dtypes.isdtype(src_dtype, "complex floating")
and _dtypes.isdtype(dtype, ("integral", "real floating"))
):
raise ValueError(
"Casting from complex to non-complex dtypes is not permitted. Please "
"first use jnp.real or jnp.imag to take the real/imaginary component of "
"your input."
)
return jnp.astype(x, dtype, copy=copy, device=device)


def can_cast(from_, to, /):
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4 changes: 3 additions & 1 deletion jax/numpy/__init__.pyi
Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,8 @@ from jax._src.typing import (
Array, ArrayLike, DType, DTypeLike,
DimSize, DuckTypedArray, Shape, DeprecatedArg
)
from jax._src.sharding import Sharding
from jax._src.lib import xla_client as xc
from jax.numpy import fft as fft, linalg as linalg
from jax.sharding import Sharding as _Sharding
import numpy as _np
Expand Down Expand Up @@ -115,7 +117,7 @@ def asarray(
) -> Array: ...
def asin(x: ArrayLike, /) -> Array: ...
def asinh(x: ArrayLike, /) -> Array: ...
def astype(a: ArrayLike, dtype: Optional[DTypeLike], /, *, copy: builtins.bool = ...) -> Array: ...
def astype(a: ArrayLike, dtype: Optional[DTypeLike], /, *, copy: builtins.bool = ..., device: xc.Device | Sharding | None = ...) -> Array: ...
def atan(x: ArrayLike, /) -> Array: ...
def atan2(x: ArrayLike, y: ArrayLike, /) -> Array: ...
def atanh(x: ArrayLike, /) -> Array: ...
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20 changes: 20 additions & 0 deletions tests/lax_numpy_test.py
Original file line number Diff line number Diff line change
Expand Up @@ -3870,6 +3870,26 @@ def testAstypeBool(self, from_dtype, use_method, to_dtype='bool'):
self._CheckAgainstNumpy(np_op, jnp_op, args_maker)
self._CompileAndCheck(jnp_op, args_maker)

@jtu.sample_product(
change_dtype=[True, False],
copy=[True, False],
)
def testAstypeCopy(self, change_dtype, copy):
dtype = 'float32' if change_dtype else 'int32'
expect_copy = change_dtype or copy
x = jnp.arange(5, dtype='int32')
y = x.astype(dtype, copy=copy)

assert y.dtype == dtype
y.delete()
assert x.is_deleted() != expect_copy

def testAstypeComplexDowncast(self):
x = jnp.array(2.0+1.5j, dtype='complex64')
msg = "Casting from complex to non-complex dtypes will soon raise "
with self.assertWarns(DeprecationWarning, msg=msg):
x.astype('float32')

def testAstypeInt4(self):
# Test converting from int4 to int8
x = np.array([1, -2, -3, 4, -8, 7], dtype=jnp.int4)
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