def get_distribution(plst: PList):
"""
Returns the distribution (as a sequential list) of its argument.
:param plst: PList
:return: list
"""
return plst.get_partition().map(len).to_seq()
def pssr(input_list: PList) -> PList:
"""
Sort the input list.
Sorts using ``<`` only.
Example::
>>> from pyske.core import PList
>>> pssr(PList.init(lambda i: 10-i, 10)).to_seq()
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
:param input_list: a parallel list.
Pre-condition: the size of the local lists should be at least
equal to the number of processors.
:return: a sorted list that is a permutation of ``input_list``.
"""
nprocs = len(par.procs())
if nprocs == 1:
return input_list.get_partition().map(sorted).flatten()
for local_size in input_list.distribution:
assert local_size >= nprocs
def permutation(index: int):
return int(index / nprocs) + nprocs * (index % nprocs)
def _sample(list_to_sample):
if list_to_sample:
size = len(list_to_sample)
step = int(size / nprocs)
return list_to_sample[step:size:step]
return []
locally_sorted = input_list.get_partition().map(sorted)
first_samples = locally_sorted.map(_sample).gather(0).get_partition()
second_samples = bcast(first_samples.map(_merge).map(_sample), 0)
slices = locally_sorted.map2(_slice, second_samples).flatten()
result = slices.permute(permutation).get_partition().map(_merge).flatten()
return result
def is_sorted(input_list: PList) -> bool:
"""Check if the list is sorted."""
return input_list.get_partition().map(_is_sorted_list).reduce(and_, True)