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Implemented NumbaExecutionEngine #61487

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1 change: 1 addition & 0 deletions doc/source/whatsnew/v3.0.0.rst
Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@ Other enhancements
^^^^^^^^^^^^^^^^^^
- :class:`pandas.api.typing.FrozenList` is available for typing the outputs of :attr:`MultiIndex.names`, :attr:`MultiIndex.codes` and :attr:`MultiIndex.levels` (:issue:`58237`)
- :class:`pandas.api.typing.SASReader` is available for typing the output of :func:`read_sas` (:issue:`55689`)
- :meth:`DataFrame.apply` accepts Numba as an engine by passing the JIT decorator directly, e.g. ``df.apply(func, engine=numba.jit)`` (:issue:`61458`)
- Added :meth:`.Styler.to_typst` to write Styler objects to file, buffer or string in Typst format (:issue:`57617`)
- Added missing :meth:`pandas.Series.info` to API reference (:issue:`60926`)
- :class:`pandas.api.typing.NoDefault` is available for typing ``no_default``
Expand Down
78 changes: 64 additions & 14 deletions pandas/core/apply.py
Original file line number Diff line number Diff line change
Expand Up @@ -178,6 +178,60 @@ def apply(
"""


class NumbaExecutionEngine(BaseExecutionEngine):
"""
Numba-based execution engine for pandas apply and map operations.
"""

@staticmethod
def map(
data: np.ndarray | Series | DataFrame,
func,
args: tuple,
kwargs: dict,
decorator: Callable | None,
skip_na: bool,
):
"""
Elementwise map for the Numba engine. Currently not supported.
"""
raise NotImplementedError("Numba map is not implemented yet.")

@staticmethod
def apply(
data: np.ndarray | Series | DataFrame,
func,
args: tuple,
kwargs: dict,
decorator: Callable,
axis: int | str,
):
"""
Apply `func` along the given axis using Numba.
"""
engine_kwargs: dict[str, bool] | None = (
decorator if isinstance(decorator, dict) else None
)

looper_args, looper_kwargs = prepare_function_arguments(
func,
args,
kwargs,
num_required_args=1,
)
# error: Argument 1 to "__call__" of "_lru_cache_wrapper" has
# incompatible type "Callable[..., Any] | str | list[Callable
# [..., Any] | str] | dict[Hashable,Callable[..., Any] | str |
# list[Callable[..., Any] | str]]"; expected "Hashable"
nb_looper = generate_apply_looper(
func,
**get_jit_arguments(engine_kwargs),
)
result = nb_looper(data, axis, *looper_args)
# If we made the result 2-D, squeeze it back to 1-D
return np.squeeze(result)


def frame_apply(
obj: DataFrame,
func: AggFuncType,
Expand Down Expand Up @@ -1094,23 +1148,19 @@ def wrapper(*args, **kwargs):
return wrapper

if engine == "numba":
args, kwargs = prepare_function_arguments(
self.func, # type: ignore[arg-type]
numba = import_optional_dependency("numba")

if not hasattr(numba.jit, "__pandas_udf__"):
numba.jit.__pandas_udf__ = NumbaExecutionEngine
Comment on lines +1153 to +1154
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What I think it'd be a simpler approach is to implement this logic here:

https://github.com/pandas-dev/pandas/blob/main/pandas/core/frame.py#L10563

There, now we are considering two cases:

  • No engine (default engine) or string engine (numba engine)
  • engine with __pandas_udf__

I would simplify that and just support engines with the engine interface __pandas_udf__:

  • No engine
  • __pandas_udf__

Since we want to support engine="numba" for now, for compatibility reasons, what I would do is immediately after DataFrame.apply is called, convert the "numba" string to a "fake" numba decorator with the __pandas_udf__ containing the the NumaExecutionEngine class. Something like:

def apply(...):
    if engine == "numba":
        numba = import_optional_dependency("numba")
        numba_jit = numba.jit(**engine_kwargs)
        numba_jit.__pandas_udf__ = NumbaExecutionEngine

From this point, all the code can pretend engine is going to be None for the default Python engine, or a __pandas_udf__ class, which should make things significantly.

The challenge is that numba and the default engine share some code, and with this approach they'll be running independently. The default engine won't know anything about an engine parameter, and the numba engine will run NumbaExecutionEngine.apply. If we don't want to repeat code, we'll probably have to restructure a bit the code, so some functions are generic and called by both engines.

When we move the default engine to a PythonExecutionEngine class, maybe it's a good idea to have the base class with the code reused by different engines. But I think that change is to big to address in a single PR, so I'd see what can be done for now that it's not too big of a change.

Does this approach makes sense to you?


result = numba.jit.__pandas_udf__.apply(
self.values,
self.func,
self.args,
self.kwargs,
num_required_args=1,
)
# error: Argument 1 to "__call__" of "_lru_cache_wrapper" has
# incompatible type "Callable[..., Any] | str | list[Callable
# [..., Any] | str] | dict[Hashable,Callable[..., Any] | str |
# list[Callable[..., Any] | str]]"; expected "Hashable"
nb_looper = generate_apply_looper(
self.func, # type: ignore[arg-type]
**get_jit_arguments(engine_kwargs),
engine_kwargs,
self.axis,
)
result = nb_looper(self.values, self.axis, *args)
# If we made the result 2-D, squeeze it back to 1-D
result = np.squeeze(result)
else:
result = np.apply_along_axis(
wrap_function(self.func),
Expand Down
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