#14506: Echelonize leads to wrong multiplication
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Reporter: mraum | Owner: jason, was
Type: defect | Status: new
Priority: critical | Milestone: sage-5.10
Component: linear algebra | Keywords:
Work issues: | Report Upstream: N/A
Reviewers: | Authors:
Merged in: | Dependencies:
Stopgaps: |
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Load the two matrices that I have attached and run the following code to
see that the second row of the second matrix is not updated correctly.
{{{
sage: (a, b) = load("tst.sobj")
sage: a.transpose() * b
[ 0 1
24 324 3200
25650 176256 1073720
5930496 30178575 143184000
639249300 2705114880 10916609264
42224364768 157237849404 565928955336
1975748911989 6712360813296 22258958382384
72248546142576 230126686576596 720999820523680
2226607404115308 6790183423299432 20478994820181329
61157329008540264 181004375431019448 531238661914490832
1546662807633726456 4467428806660680816 12801302700703268916
36384312930487005696 102550540165931773881 286559332427090336280
793661555641170811488 2178228257908531278912 5922967390221653096898
15954542776854757733856 42569726135569471713636
112504969550911913199256 294509000583368778593058
763659353026853825886576 1961586226496587115127844
4991900581029733007609328]
sage: (b.transpose() * a).transpose()
[0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0]
}}}
The following works correctly. To me this indicates that the internal
representation is somehow not updated correctly.
{{{
sage: (a, b) = load("tst.sobj")
sage: b = copy(b)
sage: a.transpose() * b
[0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0]
}}}
I make this a critical ticket. But the actual mistake seems so dangerous
and it results from a common operation, so that it is a candidate for a
blocker.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14506>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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