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# encoding: utf-8
"""Classes used in scattering and gathering sequences.
Scattering consists of partitioning a sequence and sending the various
pieces to individual nodes in a cluster.
Authors:
* Brian Granger
* MinRK
"""
#-------------------------------------------------------------------------------
# Copyright (C) 2008-2011 The IPython Development Team
#
# Distributed under the terms of the BSD License. The full license is in
# the file COPYING, distributed as part of this software.
#-------------------------------------------------------------------------------
#-------------------------------------------------------------------------------
# Imports
#-------------------------------------------------------------------------------
from __future__ import division
import types
from itertools import islice
from IPython.utils.data import flatten as utils_flatten
#-------------------------------------------------------------------------------
# Figure out which array packages are present and their array types
#-------------------------------------------------------------------------------
arrayModules = []
try:
import Numeric
except ImportError:
pass
else:
arrayModules.append({'module':Numeric, 'type':Numeric.arraytype})
try:
import numpy
except ImportError:
pass
else:
arrayModules.append({'module':numpy, 'type':numpy.ndarray})
try:
import numarray
except ImportError:
pass
else:
arrayModules.append({'module':numarray,
'type':numarray.numarraycore.NumArray})
class Map:
"""A class for partitioning a sequence using a map."""
def getPartition(self, seq, p, q):
"""Returns the pth partition of q partitions of seq."""
# Test for error conditions here
if p<0 or p>=q:
print "No partition exists."
return
remainder = len(seq)%q
basesize = len(seq)//q
hi = []
lo = []
for n in range(q):
if n < remainder:
lo.append(n * (basesize + 1))
hi.append(lo[-1] + basesize + 1)
else:
lo.append(n*basesize + remainder)
hi.append(lo[-1] + basesize)
try:
result = seq[lo[p]:hi[p]]
except TypeError:
# some objects (iterators) can't be sliced,
# use islice:
result = list(islice(seq, lo[p], hi[p]))
return result
def joinPartitions(self, listOfPartitions):
return self.concatenate(listOfPartitions)
def concatenate(self, listOfPartitions):
testObject = listOfPartitions[0]
# First see if we have a known array type
for m in arrayModules:
#print m
if isinstance(testObject, m['type']):
return m['module'].concatenate(listOfPartitions)
# Next try for Python sequence types
if isinstance(testObject, (types.ListType, types.TupleType)):
return utils_flatten(listOfPartitions)
# If we have scalars, just return listOfPartitions
return listOfPartitions
class RoundRobinMap(Map):
"""Partitions a sequence in a roun robin fashion.
This currently does not work!
"""
def getPartition(self, seq, p, q):
# if not isinstance(seq,(list,tuple)):
# raise NotImplementedError("cannot RR partition type %s"%type(seq))
return seq[p:len(seq):q]
#result = []
#for i in range(p,len(seq),q):
# result.append(seq[i])
#return result
def joinPartitions(self, listOfPartitions):
testObject = listOfPartitions[0]
# First see if we have a known array type
for m in arrayModules:
#print m
if isinstance(testObject, m['type']):
return self.flatten_array(m['type'], listOfPartitions)
if isinstance(testObject, (types.ListType, types.TupleType)):
return self.flatten_list(listOfPartitions)
return listOfPartitions
def flatten_array(self, klass, listOfPartitions):
test = listOfPartitions[0]
shape = list(test.shape)
shape[0] = sum([ p.shape[0] for p in listOfPartitions])
A = klass(shape)
N = shape[0]
q = len(listOfPartitions)
for p,part in enumerate(listOfPartitions):
A[p:N:q] = part
return A
def flatten_list(self, listOfPartitions):
flat = []
for i in range(len(listOfPartitions[0])):
flat.extend([ part[i] for part in listOfPartitions if len(part) > i ])
return flat
#lengths = [len(x) for x in listOfPartitions]
#maxPartitionLength = len(listOfPartitions[0])
#numberOfPartitions = len(listOfPartitions)
#concat = self.concatenate(listOfPartitions)
#totalLength = len(concat)
#result = []
#for i in range(maxPartitionLength):
# result.append(concat[i:totalLength:maxPartitionLength])
# return self.concatenate(listOfPartitions)
def mappable(obj):
"""return whether an object is mappable or not."""
if isinstance(obj, (tuple,list)):
return True
for m in arrayModules:
if isinstance(obj,m['type']):
return True
return False
dists = {'b':Map,'r':RoundRobinMap}
|
