#8276: Make the one(), identity_matrix() and zero_matrix() cached and immutable.
------------------------------+---------------------------------------------
Reporter: hivert | Owner: hivert
Type: defect | Status: needs_review
Priority: major | Milestone: sage-4.3.3
Component: linear algebra | Keywords: One mutable.
Author: Florent Hivert | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
------------------------------+---------------------------------------------
Comment(by rossk):
Applied the following patches (in the order below).[[BR]]
trac_8276-MatrixSpace_one-fh.patch[[BR]]
trac_8276-fix_sagelib-fh.patch[[BR]]
trac_8276-fix_zero_matrix_creation-fh.patch[[BR]]
trac_8294-matrix_2x2_copy_mutability_fix-fh.patch[[BR]]
*Almost* everything seems straightforward and correct but... Seems that
MM(0) which has a "mutable == True" property/value should be updatable but
the example "MM(0)[1,2] = 3" doesnt update MM(0) (see example below) Is
that right?[[BR]]
{{{
# prepatch responses
sage: sage: MM = MatrixSpace(ZZ, 3,3)
sage: sage: MM(0).is_mutable()
True
sage: sage: MM.zero_matrix().is_mutable()
True
sage: sage: MM(1).is_mutable()
True
sage: sage: MM.identity_matrix().is_mutable()
True
sage: sage: timeit("MM(0)")
625 loops, best of 3: 51.1 µs per loop
sage: sage: timeit("copy(MM.zero_matrix())")
625 loops, best of 3: 19.3 µs per loop
sage: sage: timeit("MM(1)")
625 loops, best of 3: 65 µs per loop
sage: sage: timeit("copy(MM.identity_matrix())")
625 loops, best of 3: 60.7 µs per loop
# postpatch responses
sage: MM = MatrixSpace(ZZ, 3,3)
sage: MM(0).is_mutable()
True
sage: MM.zero_matrix().is_mutable()
False
sage: MM(1).is_mutable()
True
sage: MM.identity_matrix().is_mutable()
False
sage: timeit("MM(0)")
625 loops, best of 3: 35.9 µs per loop
sage: timeit("copy(MM.zero_matrix())")
625 loops, best of 3: 29.3 µs per loop
sage: timeit("MM(1)")
625 loops, best of 3: 46.1 µs per loop
sage: timeit("copy(MM.identity_matrix())")
625 loops, best of 3: 29.9 µs per loop
sage: MM(0)
[0 0 0]
[0 0 0]
[0 0 0]
sage: MM(0)[1,2]=3
# this behavior is the same before and after patches were applied
# is this right? isnt MM(0) mutable and should be = 3 at row/col=[1,2]?
sage: MM(0)
[0 0 0]
[0 0 0]
[0 0 0]
sage: MM.zero_matrix()[1,2]=3
---------------------------------------------------------------------------
ValueError Traceback (most recent call
last)
/mnt/usb1/scratch/rossk/sage-4.3.3.alpha1-sage.math.washington.edu-x86_64-Linux/<ipython
console> in <module>()
/mnt/usb1/scratch/rossk/sage-4.3.3.alpha1-sage.math.washington.edu-x86_64-Linux/local/lib/python2.6
/site-packages/sage/matrix/matrix0.so in
sage.matrix.matrix0.Matrix.__setitem__ (sage/matrix/matrix0.c:5496)()
/mnt/usb1/scratch/rossk/sage-4.3.3.alpha1-sage.math.washington.edu-x86_64-Linux/local/lib/python2.6
/site-packages/sage/matrix/matrix0.so in
sage.matrix.matrix0.Matrix.check_mutability (sage/matrix/matrix0.c:3686)()
ValueError: matrix is immutable; please change a copy instead (i.e., use
copy(M) to change a copy of M).
# a copy is mutable
sage: a=copy(MM.zero_matrix())
sage: a[1,2]=3
sage: a
[0 0 0]
[0 0 3]
[0 0 0]
# here, alias_zero is pointing to same object hence it is also immutable
and correctly crashes also
sage: alias_zero = MM.zero_matrix()
sage: alias_zero[1,2]=3
---------------------------------------------------------------------------
ValueError Traceback (most recent call
last)
/mnt/usb1/scratch/rossk/sage-4.3.3.alpha1-sage.math.washington.edu-x86_64-Linux/<ipython
console> in <module>()
/mnt/usb1/scratch/rossk/sage-4.3.3.alpha1-sage.math.washington.edu-x86_64-Linux/local/lib/python2.6
/site-packages/sage/matrix/matrix0.so in
sage.matrix.matrix0.Matrix.__setitem__ (sage/matrix/matrix0.c:5496)()
/mnt/usb1/scratch/rossk/sage-4.3.3.alpha1-sage.math.washington.edu-x86_64-Linux/local/lib/python2.6
/site-packages/sage/matrix/matrix0.so in
sage.matrix.matrix0.Matrix.check_mutability (sage/matrix/matrix0.c:3686)()
ValueError: matrix is immutable; please change a copy instead (i.e., use
copy(M) to change a copy of M).
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8276#comment:12>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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