calling split_result_of_axis_func_pandas only for ray

Signed-off-by: arunjose696 <arunjose696@gmail.com>

Author: arunjose696

modin/core/dataframe/pandas/partitioning/axis_partition.py

@@ -21,7 +21,10 @@
 from modin.core.dataframe.base.partitioning.axis_partition import (
     BaseDataframeAxisPartition,
 )
-from modin.core.storage_formats.pandas.utils import split_result_of_axis_func_pandas
+from modin.core.storage_formats.pandas.utils import (
+    generate_result_of_axis_func_pandas,
+    split_result_of_axis_func_pandas,
+)
 
 from .partition import PandasDataframePartition
 
@@ -388,6 +391,7 @@ def deploy_axis_func(
         *partitions,
         lengths=None,
         manual_partition=False,
+        return_generator=False,
     ):
         """
         Deploy a function along a full axis.
@@ -413,11 +417,14 @@ def deploy_axis_func(
             The list of lengths to shuffle the object.
         manual_partition : bool, default: False
             If True, partition the result with `lengths`.
+        return_generator : bool, default: False
+            Return a generator from the function, set to `True` for Ray backend
+            as Ray remote functions can return Generators.
 
         Returns
         -------
-        list
-            A list of pandas DataFrames.
+        list | Generator
+            A list or generator of pandas DataFrames.
         """
         dataframe = pandas.concat(list(partitions), axis=axis, copy=False)
         with warnings.catch_warnings():
@@ -451,7 +458,12 @@ def deploy_axis_func(
                 lengths = [len(part.columns) for part in partitions]
                 if sum(lengths) != len(result.columns):
                     lengths = None
-        return split_result_of_axis_func_pandas(axis, num_splits, result, lengths)
+        if return_generator:
+            return generate_result_of_axis_func_pandas(
+                axis, num_splits, result, lengths
+            )
+        else:
+            return split_result_of_axis_func_pandas(axis, num_splits, result, lengths)
 
     @classmethod
     def deploy_func_between_two_axis_partitions(
@@ -464,6 +476,7 @@ def deploy_func_between_two_axis_partitions(
         len_of_left,
         other_shape,
         *partitions,
+        return_generator=False,
     ):
         """
         Deploy a function along a full axis between two data sets.
@@ -487,11 +500,14 @@ def deploy_func_between_two_axis_partitions(
             (other_shape[i-1], other_shape[i]) will indicate slice to restore i-1 axis partition.
         *partitions : iterable
             All partitions that make up the full axis (row or column) for both data sets.
+        return_generator : bool, default: False
+            Return a generator from the function, set to `True` for Ray backend
+            as Ray remote functions can return Generators.
 
         Returns
         -------
-        list
-            A list of pandas DataFrames.
+        list | Generator
+            A list or generator of pandas DataFrames.
         """
         lt_frame = pandas.concat(partitions[:len_of_left], axis=axis, copy=False)
 
@@ -510,7 +526,18 @@ def deploy_func_between_two_axis_partitions(
         with warnings.catch_warnings():
             warnings.filterwarnings("ignore", category=FutureWarning)
             result = func(lt_frame, rt_frame, *f_args, **f_kwargs)
-        return split_result_of_axis_func_pandas(axis, num_splits, result)
+        if return_generator:
+            return generate_result_of_axis_func_pandas(
+                axis,
+                num_splits,
+                result,
+            )
+        else:
+            return split_result_of_axis_func_pandas(
+                axis,
+                num_splits,
+                result,
+            )
 
     @classmethod
     def drain(cls, df: pandas.DataFrame, call_queue: list):

modin/core/execution/ray/implementations/cudf_on_ray/partitioning/partition_manager.py

@@ -125,7 +125,7 @@ def from_pandas(cls, df, return_dims=False):
         num_splits = GpuCount.get()
         put_func = cls._partition_class.put
         # For now, we default to row partitioning
-        pandas_dfs = list(split_result_of_axis_func_pandas(0, num_splits, df))
+        pandas_dfs = split_result_of_axis_func_pandas(0, num_splits, df)
         keys = [
             put_func(cls._get_gpu_managers()[i], pandas_dfs[i])
             for i in range(num_splits)

modin/core/execution/ray/implementations/pandas_on_ray/partitioning/virtual_partition.py

@@ -189,6 +189,7 @@ def deploy_axis_func(
             f_kwargs=f_kwargs,
             manual_partition=manual_partition,
             lengths=lengths,
+            return_generator=True,
         )
 
     @classmethod
@@ -244,6 +245,7 @@ def deploy_func_between_two_axis_partitions(
             f_to_deploy=func,
             f_len_args=len(f_args),
             f_kwargs=f_kwargs,
+            return_generator=True,
         )
 
     def wait(self):

modin/core/storage_formats/cudf/parser.py

@@ -39,7 +39,9 @@ def _split_result_for_readers(axis, num_splits, df):  # pragma: no cover
     Returns:
         A list of pandas DataFrames.
     """
-    splits = list(split_result_of_axis_func_pandas(axis, num_splits, df))
+    splits = split_result_of_axis_func_pandas(axis, num_splits, df)
+    if not isinstance(splits, list):
+        splits = [splits]
     return splits
 
 

modin/core/storage_formats/pandas/parsers.py

@@ -113,7 +113,9 @@ def _split_result_for_readers(axis, num_splits, df):  # pragma: no cover
     list
         A list of pandas DataFrames.
     """
-    splits = list(split_result_of_axis_func_pandas(axis, num_splits, df))
+    splits = split_result_of_axis_func_pandas(axis, num_splits, df)
+    if not isinstance(splits, list):
+        splits = [splits]
     return splits
 
 

modin/core/storage_formats/pandas/utils.py

@@ -84,11 +84,70 @@ def split_result_of_axis_func_pandas(
     list of pandas.DataFrames
         Splitted dataframe represented by list of frames.
     """
+    if num_splits == 1:
+        return [result]
+
+    if length_list is None:
+        length_list = get_length_list(result.shape[axis], num_splits, min_block_size)
+    # Inserting the first "zero" to properly compute cumsum indexing slices
+    length_list = np.insert(length_list, obj=0, values=[0])
+
+    sums = np.cumsum(length_list)
+    axis = 0 if isinstance(result, pandas.Series) else axis
+    # We do this to restore block partitioning
+    if axis == 0:
+        chunked = [result.iloc[sums[i] : sums[i + 1]] for i in range(len(sums) - 1)]
+    else:
+        chunked = [result.iloc[:, sums[i] : sums[i + 1]] for i in range(len(sums) - 1)]
+
+    return [
+        # Sliced MultiIndex still stores all encoded values of the original index, explicitly
+        # asking it to drop unused values in order to save memory.
+        (
+            chunk.set_axis(
+                chunk.axes[axis].remove_unused_levels(), axis=axis, copy=False
+            )
+            if isinstance(chunk.axes[axis], pandas.MultiIndex)
+            else chunk
+        )
+        for chunk in chunked
+    ]
+
+
+def generate_result_of_axis_func_pandas(
+    axis, num_splits, result, length_list=None, min_block_size=None
+):
+    """
+    Generate pandas DataFrame evenly based on the provided number of splits.
+
+    Parameters
+    ----------
+    axis : {0, 1}
+        Axis to split across. 0 means index axis when 1 means column axis.
+    num_splits : int
+        Number of splits to separate the DataFrame into.
+        This parameter is ignored if `length_list` is specified.
+    result : pandas.DataFrame
+        DataFrame to split.
+    length_list : list of ints, optional
+        List of slice lengths to split DataFrame into. This is used to
+        return the DataFrame to its original partitioning schema.
+    min_block_size : int, optional
+        Minimum number of rows/columns in a single split.
+        If not specified, the value is assumed equal to ``MinPartitionSize``.
+
+    Yields
+    ------
+    Generator
+        Generates 'num_splits' dataframes as a result of axis function.
+    """
     if num_splits == 1:
         yield result
     else:
         if length_list is None:
-            length_list = get_length_list(result.shape[axis], num_splits,min_block_size)
+            length_list = get_length_list(
+                result.shape[axis], num_splits, min_block_size
+            )
         # Inserting the first "zero" to properly compute cumsum indexing slices
         length_list = np.insert(length_list, obj=0, values=[0])
         sums = np.cumsum(length_list)