# -*- coding: utf-8 -*-
# Copyright (C) 2011-2017 Martin Sandve Alnæs
#
# This file is part of UFLACS.
#
# UFLACS is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# UFLACS is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with UFLACS. If not, see <http://www.gnu.org/licenses/>
"""Compressed row storage 'matrix' (actually just a non-rectangular 2d array)."""
import numpy
[docs]def sufficient_int(maxval):
return numpy.int16 if maxval < 2**15 else numpy.int32
[docs]class CRSArray(object):
"""An array of variable length dense arrays.
Stored efficiently with simple compressed row storage.
This CRS array variant doesn't have a sparsity pattern,
as each row is simply a dense vector.
Values are stored in one flat array 'data[]',
and 'row_offsets[i]' contains the index to the first
element on row i for 0<=i<=num_rows.
There is no column index.
"""
def __init__(self, row_capacity, element_capacity, dtype):
itype = sufficient_int(element_capacity)
self.row_offsets = numpy.zeros(row_capacity + 1, dtype=itype)
self.data = numpy.zeros(element_capacity, dtype=dtype)
self.num_rows = 0
[docs] def push_row(self, elements):
a = self.row_offsets[self.num_rows]
b = a + len(elements)
self.data[a:b] = elements
self.num_rows += 1
self.row_offsets[self.num_rows] = b
@property
def num_elements(self):
return self.row_offsets[self.num_rows]
def __getitem__(self, row):
if row < 0 or row >= self.num_rows:
raise IndexError("Row number out of range!")
a = self.row_offsets[row]
b = self.row_offsets[row + 1]
return self.data[a:b]
def __len__(self):
return self.num_rows
def __str__(self):
return "[%s]" % ('\n'.join(str(row) for row in self),)
[docs] @classmethod
def from_rows(cls, rows, num_rows, num_elements, dtype):
"Construct a CRSArray from a list of row element lists."
crs = CRSArray(num_rows, num_elements, dtype)
for row in rows:
crs.push_row(row)
return crs