436 lines
14 KiB
Python
436 lines
14 KiB
Python
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# This file is part of h5py, a Python interface to the HDF5 library.
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#
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# http://www.h5py.org
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#
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# Copyright 2008-2013 Andrew Collette and contributors
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#
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# License: Standard 3-clause BSD; see "license.txt" for full license terms
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# and contributor agreement.
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"""
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High-level access to HDF5 dataspace selections
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"""
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import numpy as np
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from .base import product
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from .. import h5s, h5r, _selector
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def select(shape, args, dataset=None):
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""" High-level routine to generate a selection from arbitrary arguments
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to __getitem__. The arguments should be the following:
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shape
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Shape of the "source" dataspace.
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args
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Either a single argument or a tuple of arguments. See below for
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supported classes of argument.
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dataset
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A h5py.Dataset instance representing the source dataset.
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Argument classes:
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Single Selection instance
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Returns the argument.
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numpy.ndarray
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Must be a boolean mask. Returns a PointSelection instance.
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RegionReference
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Returns a Selection instance.
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Indices, slices, ellipses, MultiBlockSlices only
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Returns a SimpleSelection instance
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Indices, slices, ellipses, lists or boolean index arrays
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Returns a FancySelection instance.
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"""
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if not isinstance(args, tuple):
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args = (args,)
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# "Special" indexing objects
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if len(args) == 1:
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arg = args[0]
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if isinstance(arg, Selection):
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if arg.shape != shape:
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raise TypeError("Mismatched selection shape")
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return arg
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elif isinstance(arg, np.ndarray) and arg.dtype.kind == 'b':
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if arg.shape != shape:
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raise TypeError("Boolean indexing array has incompatible shape")
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return PointSelection.from_mask(arg)
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elif isinstance(arg, h5r.RegionReference):
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if dataset is None:
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raise TypeError("Cannot apply a region reference without a dataset")
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sid = h5r.get_region(arg, dataset.id)
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if shape != sid.shape:
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raise TypeError("Reference shape does not match dataset shape")
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return Selection(shape, spaceid=sid)
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if dataset is not None:
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selector = dataset._selector
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else:
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space = h5s.create_simple(shape)
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selector = _selector.Selector(space)
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return selector.make_selection(args)
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class Selection:
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"""
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Base class for HDF5 dataspace selections. Subclasses support the
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"selection protocol", which means they have at least the following
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members:
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__init__(shape) => Create a new selection on "shape"-tuple
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__getitem__(args) => Perform a selection with the range specified.
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What args are allowed depends on the
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particular subclass in use.
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id (read-only) => h5py.h5s.SpaceID instance
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shape (read-only) => The shape of the dataspace.
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mshape (read-only) => The shape of the selection region.
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Not guaranteed to fit within "shape", although
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the total number of points is less than
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product(shape).
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nselect (read-only) => Number of selected points. Always equal to
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product(mshape).
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broadcast(target_shape) => Return an iterable which yields dataspaces
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for read, based on target_shape.
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The base class represents "unshaped" selections (1-D).
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"""
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def __init__(self, shape, spaceid=None):
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""" Create a selection. Shape may be None if spaceid is given. """
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if spaceid is not None:
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self._id = spaceid
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self._shape = spaceid.shape
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else:
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shape = tuple(shape)
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self._shape = shape
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self._id = h5s.create_simple(shape, (h5s.UNLIMITED,)*len(shape))
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self._id.select_all()
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@property
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def id(self):
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""" SpaceID instance """
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return self._id
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@property
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def shape(self):
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""" Shape of whole dataspace """
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return self._shape
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@property
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def nselect(self):
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""" Number of elements currently selected """
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return self._id.get_select_npoints()
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@property
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def mshape(self):
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""" Shape of selection (always 1-D for this class) """
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return (self.nselect,)
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@property
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def array_shape(self):
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"""Shape of array to read/write (always 1-D for this class)"""
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return self.mshape
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# expand_shape and broadcast only really make sense for SimpleSelection
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def expand_shape(self, source_shape):
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if product(source_shape) != self.nselect:
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raise TypeError("Broadcasting is not supported for point-wise selections")
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return source_shape
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def broadcast(self, source_shape):
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""" Get an iterable for broadcasting """
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if product(source_shape) != self.nselect:
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raise TypeError("Broadcasting is not supported for point-wise selections")
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yield self._id
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def __getitem__(self, args):
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raise NotImplementedError("This class does not support indexing")
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class PointSelection(Selection):
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"""
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Represents a point-wise selection. You can supply sequences of
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points to the three methods append(), prepend() and set(), or
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instantiate it with a single boolean array using from_mask().
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"""
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def __init__(self, shape, spaceid=None, points=None):
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super().__init__(shape, spaceid)
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if points is not None:
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self._perform_selection(points, h5s.SELECT_SET)
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def _perform_selection(self, points, op):
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""" Internal method which actually performs the selection """
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points = np.asarray(points, order='C', dtype='u8')
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if len(points.shape) == 1:
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points.shape = (1,points.shape[0])
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if self._id.get_select_type() != h5s.SEL_POINTS:
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op = h5s.SELECT_SET
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if len(points) == 0:
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self._id.select_none()
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else:
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self._id.select_elements(points, op)
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@classmethod
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def from_mask(cls, mask, spaceid=None):
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"""Create a point-wise selection from a NumPy boolean array """
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if not (isinstance(mask, np.ndarray) and mask.dtype.kind == 'b'):
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raise TypeError("PointSelection.from_mask only works with bool arrays")
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points = np.transpose(mask.nonzero())
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return cls(mask.shape, spaceid, points=points)
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def append(self, points):
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""" Add the sequence of points to the end of the current selection """
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self._perform_selection(points, h5s.SELECT_APPEND)
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def prepend(self, points):
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""" Add the sequence of points to the beginning of the current selection """
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self._perform_selection(points, h5s.SELECT_PREPEND)
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def set(self, points):
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""" Replace the current selection with the given sequence of points"""
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self._perform_selection(points, h5s.SELECT_SET)
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class SimpleSelection(Selection):
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""" A single "rectangular" (regular) selection composed of only slices
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and integer arguments. Can participate in broadcasting.
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"""
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@property
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def mshape(self):
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""" Shape of current selection """
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return self._sel[1]
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@property
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def array_shape(self):
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scalar = self._sel[3]
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return tuple(x for x, s in zip(self.mshape, scalar) if not s)
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def __init__(self, shape, spaceid=None, hyperslab=None):
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super().__init__(shape, spaceid)
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if hyperslab is not None:
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self._sel = hyperslab
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else:
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# No hyperslab specified - select all
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rank = len(self.shape)
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self._sel = ((0,)*rank, self.shape, (1,)*rank, (False,)*rank)
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def expand_shape(self, source_shape):
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"""Match the dimensions of an array to be broadcast to the selection
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The returned shape describes an array of the same size as the input
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shape, but its dimensions
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E.g. with a dataset shape (10, 5, 4, 2), writing like this::
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ds[..., 0] = np.ones((5, 4))
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The source shape (5, 4) will expand to (1, 5, 4, 1).
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Then the broadcast method below repeats that chunk 10
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times to write to an effective shape of (10, 5, 4, 1).
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"""
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start, count, step, scalar = self._sel
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rank = len(count)
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remaining_src_dims = list(source_shape)
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eshape = []
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for idx in range(1, rank + 1):
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if len(remaining_src_dims) == 0 or scalar[-idx]: # Skip scalar axes
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eshape.append(1)
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else:
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t = remaining_src_dims.pop()
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if t == 1 or count[-idx] == t:
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eshape.append(t)
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else:
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raise TypeError("Can't broadcast %s -> %s" % (source_shape, self.array_shape)) # array shape
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if any([n > 1 for n in remaining_src_dims]):
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# All dimensions from target_shape should either have been popped
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# to match the selection shape, or be 1.
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raise TypeError("Can't broadcast %s -> %s" % (source_shape, self.array_shape)) # array shape
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# We have built eshape backwards, so now reverse it
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return tuple(eshape[::-1])
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def broadcast(self, source_shape):
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""" Return an iterator over target dataspaces for broadcasting.
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Follows the standard NumPy broadcasting rules against the current
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selection shape (self.mshape).
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"""
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if self.shape == ():
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if product(source_shape) != 1:
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raise TypeError("Can't broadcast %s to scalar" % source_shape)
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self._id.select_all()
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yield self._id
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return
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start, count, step, scalar = self._sel
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rank = len(count)
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tshape = self.expand_shape(source_shape)
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chunks = tuple(x//y for x, y in zip(count, tshape))
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nchunks = product(chunks)
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if nchunks == 1:
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yield self._id
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else:
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sid = self._id.copy()
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sid.select_hyperslab((0,)*rank, tshape, step)
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for idx in range(nchunks):
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offset = tuple(x*y*z + s for x, y, z, s in zip(np.unravel_index(idx, chunks), tshape, step, start))
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sid.offset_simple(offset)
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yield sid
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class FancySelection(Selection):
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"""
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Implements advanced NumPy-style selection operations in addition to
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the standard slice-and-int behavior.
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Indexing arguments may be ints, slices, lists of indices, or
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per-axis (1D) boolean arrays.
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Broadcasting is not supported for these selections.
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"""
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@property
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def mshape(self):
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return self._mshape
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@property
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def array_shape(self):
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return self._array_shape
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def __init__(self, shape, spaceid=None, mshape=None, array_shape=None):
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super().__init__(shape, spaceid)
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if mshape is None:
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mshape = self.shape
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if array_shape is None:
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array_shape = mshape
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self._mshape = mshape
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self._array_shape = array_shape
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def expand_shape(self, source_shape):
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if not source_shape == self.array_shape:
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raise TypeError("Broadcasting is not supported for complex selections")
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return source_shape
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def broadcast(self, source_shape):
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if not source_shape == self.array_shape:
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raise TypeError("Broadcasting is not supported for complex selections")
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yield self._id
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def guess_shape(sid):
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""" Given a dataspace, try to deduce the shape of the selection.
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Returns one of:
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* A tuple with the selection shape, same length as the dataspace
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* A 1D selection shape for point-based and multiple-hyperslab selections
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* None, for unselected scalars and for NULL dataspaces
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"""
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sel_class = sid.get_simple_extent_type() # Dataspace class
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sel_type = sid.get_select_type() # Flavor of selection in use
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if sel_class == h5s.NULL:
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# NULL dataspaces don't support selections
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return None
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elif sel_class == h5s.SCALAR:
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# NumPy has no way of expressing empty 0-rank selections, so we use None
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if sel_type == h5s.SEL_NONE: return None
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if sel_type == h5s.SEL_ALL: return tuple()
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elif sel_class != h5s.SIMPLE:
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raise TypeError("Unrecognized dataspace class %s" % sel_class)
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# We have a "simple" (rank >= 1) dataspace
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N = sid.get_select_npoints()
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rank = len(sid.shape)
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if sel_type == h5s.SEL_NONE:
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return (0,)*rank
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elif sel_type == h5s.SEL_ALL:
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return sid.shape
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elif sel_type == h5s.SEL_POINTS:
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# Like NumPy, point-based selections yield 1D arrays regardless of
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# the dataspace rank
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return (N,)
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elif sel_type != h5s.SEL_HYPERSLABS:
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raise TypeError("Unrecognized selection method %s" % sel_type)
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# We have a hyperslab-based selection
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if N == 0:
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||
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|
return (0,)*rank
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||
|
|
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||
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|
bottomcorner, topcorner = (np.array(x) for x in sid.get_select_bounds())
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||
|
|
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||
|
|
# Shape of full selection box
|
||
|
|
boxshape = topcorner - bottomcorner + np.ones((rank,))
|
||
|
|
|
||
|
|
def get_n_axis(sid, axis):
|
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|
|
""" Determine the number of elements selected along a particular axis.
|
||
|
|
|
||
|
|
To do this, we "mask off" the axis by making a hyperslab selection
|
||
|
|
which leaves only the first point along the axis. For a 2D dataset
|
||
|
|
with selection box shape (X, Y), for axis 1, this would leave a
|
||
|
|
selection of shape (X, 1). We count the number of points N_leftover
|
||
|
|
remaining in the selection and compute the axis selection length by
|
||
|
|
N_axis = N/N_leftover.
|
||
|
|
"""
|
||
|
|
|
||
|
|
if(boxshape[axis]) == 1:
|
||
|
|
return 1
|
||
|
|
|
||
|
|
start = bottomcorner.copy()
|
||
|
|
start[axis] += 1
|
||
|
|
count = boxshape.copy()
|
||
|
|
count[axis] -= 1
|
||
|
|
|
||
|
|
# Throw away all points along this axis
|
||
|
|
masked_sid = sid.copy()
|
||
|
|
masked_sid.select_hyperslab(tuple(start), tuple(count), op=h5s.SELECT_NOTB)
|
||
|
|
|
||
|
|
N_leftover = masked_sid.get_select_npoints()
|
||
|
|
|
||
|
|
return N//N_leftover
|
||
|
|
|
||
|
|
|
||
|
|
shape = tuple(get_n_axis(sid, x) for x in range(rank))
|
||
|
|
|
||
|
|
if product(shape) != N:
|
||
|
|
# This means multiple hyperslab selections are in effect,
|
||
|
|
# so we fall back to a 1D shape
|
||
|
|
return (N,)
|
||
|
|
|
||
|
|
return shape
|