Commit 6a5dfefa by Kirill Smelkov

bigarray: Factor-out our custom numpy.lib.stride_tricks.as_strided-alike into lib/xnumpy.py

We are going to use this code in another place, so move this out to
dommon place as a preparatory step first.

On a related note: Since ArrayRef is generic and quite independent from
BigArray (it only supports it, but equally it supports just other - e.g.
plain arrays), the proper place for it might be also to be lib/xnumpy.py .
We might get to this topic a bit later.
1 parent 99b91c84
......@@ -38,8 +38,8 @@ of physical RAM.
from __future__ import print_function
from wendelin.lib.calc import mul
from wendelin.lib.xnumpy import _as_strided
from numpy import ndarray, dtype, sign, newaxis, asarray, argmax, uint8
from numpy.lib.stride_tricks import DummyArray
import logging
......@@ -618,29 +618,7 @@ class ArrayRef(object):
#
# it is also safe because we checked .shape and .stridev not to escape
# from bchild data buffer.
#
# the code below is very close to
#
# a = stride_tricks.as_strided(bchild_z0, shape=self.shape, strides=self.stridev)
#
# but we don't use as_strided() because we also have to change dtype
# with shape and strides in one go - else changing dtype after either
# via a.dtype = ..., or via a.view(dtype=...) can raise errors like
#
# "When changing to a larger dtype, its size must be a
# divisor of the total size in bytes of the last axis
# of the array."
aiface = dict(bchild_z0.__array_interface__)
aiface['shape'] = tuple(self.shape)
aiface['strides'] = tuple(self.stridev)
# type: for now we only care that itemsize is the same
aiface['typestr'] = '|V%d' % self.dtype.itemsize
aiface['descr'] = [('', aiface['typestr'])]
a = asarray(DummyArray(aiface, base=bchild_z0))
# restore full dtype - it should not raise here, since itemsize is the same
a.dtype = self.dtype
a = _as_strided(bchild_z0, tuple(self.shape), tuple(self.stridev), self.dtype)
# restore full array type
a = a.view(type=self.atype)
......
# -*- coding: utf-8 -*-
# NumPy-related utilities
# Copyright (C) 2018 Nexedi SA and Contributors.
# Kirill Smelkov <kirr@nexedi.com>
#
# This program is free software: you can Use, Study, Modify and Redistribute
# it under the terms of the GNU General Public License version 3, or (at your
# option) any later version, as published by the Free Software Foundation.
#
# You can also Link and Combine this program with other software covered by
# the terms of any of the Free Software licenses or any of the Open Source
# Initiative approved licenses and Convey the resulting work. Corresponding
# source of such a combination shall include the source code for all other
# software used.
#
# This program is distributed WITHOUT ANY WARRANTY; without even the implied
# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
#
# See COPYING file for full licensing terms.
# See https://www.nexedi.com/licensing for rationale and options.
import numpy as np
from numpy.lib import stride_tricks as npst
# _as_strided is similar to numpy.lib.stride_tricks.as_strided, but allows to
# set all shape/stridev/dtype in one go.
#
# It must be used with extreme care, because if there is math error in the
# arguments, the resulting array can cover wrong memory. Bugs here thus can
# lead to mysterious crashes.
def _as_strided(arr, shape, stridev, dtype):
# the code below is very close to
#
# a = stride_tricks.as_strided(arr, shape=shape, strides=stridev)
#
# but we don't use as_strided() because we also have to change dtype
# with shape and strides in one go - else changing dtype after either
# via a.dtype = ..., or via a.view(dtype=...) can raise errors like
#
# "When changing to a larger dtype, its size must be a
# divisor of the total size in bytes of the last axis
# of the array."
aiface = dict(arr.__array_interface__)
aiface['shape'] = shape
aiface['strides'] = stridev
# type: for now we only care that itemsize is the same
aiface['typestr'] = '|V%d' % dtype.itemsize
aiface['descr'] = [('', aiface['typestr'])]
a = np.asarray(npst.DummyArray(aiface, base=arr))
# restore full dtype - it should not raise here, since itemsize is the same
a.dtype = dtype
# restore full array type (mimics subok=True)
if type(a) is not type(arr):
a = a.view(type=type(arr))
# we are done
return a
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