Migrate round to pylibcudf (#15863)

xref #15162

Migrate round.pxd to use pylibcudf APIs.

Authors:
  - Thomas Li (https://github.com/lithomas1)

Approvers:
  - https://github.com/brandon-b-miller
  - Lawrence Mitchell (https://github.com/wence-)

URL: #15863

docs/cudf/source/user_guide/api_docs/pylibcudf/index.rst

@@ -22,6 +22,7 @@ This page provides API documentation for pylibcudf.
     reduce
     reshape
     rolling
+    round
     scalar
     search
     stream_compaction

docs/cudf/source/user_guide/api_docs/pylibcudf/round.rst

@@ -0,0 +1,6 @@
+=====
+round
+=====
+
+.. automodule:: cudf._lib.pylibcudf.round
+   :members:

python/cudf/cudf/_lib/pylibcudf/CMakeLists.txt

@@ -29,6 +29,7 @@ set(cython_sources
     replace.pyx
     reshape.pyx
     rolling.pyx
+    round.pyx
     scalar.pyx
     search.pyx
     stream_compaction.pyx

python/cudf/cudf/_lib/pylibcudf/__init__.pxd

@@ -15,6 +15,7 @@ from . cimport (
     replace,
     reshape,
     rolling,
+    round,
     search,
     sorting,
     stream_compaction,
@@ -48,6 +49,7 @@ __all__ = [
     "reduce",
     "replace",
     "rolling",
+    "round",
     "search",
     "stream_compaction",
     "strings",

python/cudf/cudf/_lib/pylibcudf/__init__.py

@@ -15,6 +15,7 @@
     replace,
     reshape,
     rolling,
+    round,
     search,
     sorting,
     stream_compaction,
@@ -48,6 +49,7 @@
     "reduce",
     "replace",
     "rolling",
+    "round",
     "search",
     "stream_compaction",
     "strings",

python/cudf/cudf/_lib/pylibcudf/libcudf/CMakeLists.txt

@@ -12,7 +12,7 @@
 # the License.
 # =============================================================================
 
-set(cython_sources aggregation.pyx binaryop.pyx copying.pyx replace.pyx reduce.pxd
+set(cython_sources aggregation.pyx binaryop.pyx copying.pyx replace.pyx reduce.pxd round.pyx
                    stream_compaction.pyx types.pyx unary.pyx
 )
 

python/cudf/cudf/_lib/pylibcudf/libcudf/round.pxd

@@ -9,9 +9,9 @@ from cudf._lib.pylibcudf.libcudf.column.column_view cimport column_view
 
 cdef extern from "cudf/round.hpp" namespace "cudf" nogil:
 
-    ctypedef enum rounding_method "cudf::rounding_method":
-        HALF_UP "cudf::rounding_method::HALF_UP"
-        HALF_EVEN "cudf::rounding_method::HALF_EVEN"
+    cpdef enum class rounding_method(int32_t):
+        HALF_UP
+        HALF_EVEN
 
     cdef unique_ptr[column] round (
         const column_view& input,

python/cudf/cudf/_lib/pylibcudf/round.pxd

@@ -0,0 +1,13 @@
+# Copyright (c) 2024, NVIDIA CORPORATION.
+from libc.stdint cimport int32_t
+
+from cudf._lib.pylibcudf.libcudf.round cimport rounding_method
+
+from .column cimport Column
+
+
+cpdef Column round(
+    Column source,
+    int32_t decimal_places = *,
+    rounding_method round_method = *
+)

python/cudf/cudf/_lib/pylibcudf/round.pyx

@@ -0,0 +1,54 @@
+# Copyright (c) 2024, NVIDIA CORPORATION.
+from libc.stdint cimport int32_t
+from libcpp.memory cimport unique_ptr
+from libcpp.utility cimport move
+
+from cudf._lib.pylibcudf.libcudf.round cimport (
+    round as cpp_round,
+    rounding_method,
+)
+
+from cudf._lib.pylibcudf.libcudf.round import \
+    rounding_method as RoundingMethod  # no-cython-lint
+
+from cudf._lib.pylibcudf.libcudf.column.column cimport column
+
+from .column cimport Column
+
+
+cpdef Column round(
+    Column source,
+    int32_t decimal_places = 0,
+    rounding_method round_method = rounding_method.HALF_UP
+):
+    """Rounds all the values in a column to the specified number of decimal places.
+
+    For details, see :cpp:func:`round`.
+
+    Parameters
+    ----------
+    source : Column
+        The Column for which to round values.
+    decimal_places: int32_t, optional
+        The number of decimal places to round to (default 0)
+    round_method: rounding_method, optional
+        The method by which to round each value.
+        Can be one of { RoundingMethod.HALF_UP, RoundingMethod.HALF_EVEN }
+        (default rounding_method.HALF_UP)
+
+    Returns
+    -------
+    pylibcudf.Column
+        A Column with values rounded
+    """
+    cdef unique_ptr[column] c_result
+    with nogil:
+        c_result = move(
+            cpp_round(
+                source.view(),
+                decimal_places,
+                round_method
+            )
+        )
+
+    return Column.from_libcudf(move(c_result))

python/cudf/cudf/_lib/round.pyx

@@ -2,16 +2,10 @@
 
 from cudf.core.buffer import acquire_spill_lock
 
-from libcpp.memory cimport unique_ptr
-from libcpp.utility cimport move
-
 from cudf._lib.column cimport Column
-from cudf._lib.pylibcudf.libcudf.column.column cimport column
-from cudf._lib.pylibcudf.libcudf.column.column_view cimport column_view
-from cudf._lib.pylibcudf.libcudf.round cimport (
-    round as cpp_round,
-    rounding_method as cpp_rounding_method,
-)
+
+import cudf._lib.pylibcudf as plc
+from cudf._lib.pylibcudf.round import RoundingMethod
 
 
 @acquire_spill_lock()
@@ -31,19 +25,15 @@ def round(Column input_col, int decimal_places=0, how="half_even"):
     if how not in {"half_even", "half_up"}:
         raise ValueError("'how' must be either 'half_even' or 'half_up'")
 
-    cdef column_view input_col_view = input_col.view()
-    cdef unique_ptr[column] c_result
-    cdef cpp_rounding_method c_how = (
-        cpp_rounding_method.HALF_EVEN if how == "half_even"
-        else cpp_rounding_method.HALF_UP
+    how = (
+        RoundingMethod.HALF_EVEN if how == "half_even"
+        else RoundingMethod.HALF_UP
     )
-    with nogil:
-        c_result = move(
-            cpp_round(
-                input_col_view,
-                decimal_places,
-                c_how
-            )
-        )
 
-    return Column.from_unique_ptr(move(c_result))
+    return Column.from_pylibcudf(
+        plc.round.round(
+            input_col.to_pylibcudf(mode="read"),
+            decimal_places,
+            how
+        )
+    )

python/cudf/cudf/pylibcudf_tests/test_round.py

@@ -0,0 +1,38 @@
+# Copyright (c) 2024, NVIDIA CORPORATION.
+
+import pyarrow as pa
+import pytest
+from utils import assert_column_eq
+
+import cudf._lib.pylibcudf as plc
+
+
+@pytest.fixture(params=[False, True])
+def nullable(request):
+    return request.param
+
+
+@pytest.fixture(params=["float32", "float64"])
+def column(request, nullable):
+    values = [2.5, 2.49, 1.6, 8, -1.5, -1.7, -0.5, 0.5]
+    typ = {"float32": pa.float32(), "float64": pa.float64()}[request.param]
+    if nullable:
+        values[2] = None
+    return plc.interop.from_arrow(pa.array(values, type=typ))
+
+
+@pytest.mark.parametrize(
+    "round_mode", ["half_towards_infinity", "half_to_even"]
+)
+@pytest.mark.parametrize("decimals", [0, 1, 2, 5])
+def test_round(column, round_mode, decimals):
+    method = {
+        "half_towards_infinity": plc.round.RoundingMethod.HALF_UP,
+        "half_to_even": plc.round.RoundingMethod.HALF_EVEN,
+    }[round_mode]
+    got = plc.round.round(column, decimals, method)
+    expect = pa.compute.round(
+        plc.interop.to_arrow(column), decimals, round_mode
+    )
+
+    assert_column_eq(expect, got)