#19340: Better interface for hadamard_matrix
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Reporter: ncohen | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.9
Component: combinatorial | Resolution:
designs | Merged in:
Keywords: | Reviewers:
Authors: Nathann Cohen | Work issues:
Report Upstream: N/A | Commit:
Branch: u/ncohen/19340 | 247a2bb4dcec180227cd9fb9bcd331a27a289016
Dependencies: | Stopgaps:
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Comment (by ncohen):
> It should be enough (untested) to add the following declarations in
libs/flint/fmpz_mat.pxd
HMmmm.. I don't feel much at ease with adding matrix code, sorry.
Especially if it is only implemented for a specific data structure and
such.
> You may well be right about combinatorial designs in general. But,
having written the flint code, and considering that it implements a fairly
simple algorithm, when it's already exhaustively tested up to size 300, I
think it's highly unlikely to give an incorrect matrix for larger sizes.
So I can't agree with slowing it down many orders of magnitude by default.
Unless you do intend to use this code, couldn't you trust the opinion of
those who do and develop it?
I know how many hours, night and weeks I wasted because of a typo in data
or in code. You wouldn't mind slowing by "several orders of magnitude" a
function like `.__repr__` because it is never a critical. Do you generate
Hadamard matrices intensively? Furthermore you can disable the check with
'check=False'. Please don't turn this ticket into a war just because of a
check you can disable, which saved my skin innumerable times in similar
code. It's not worth it. I know it, and I need the flag. Besides, checking
the constructions is already the default for all other design
constructions.
> It doesn't have a database; it uses the Paley construction. As noted
above, you can easily use a fallback database/algorithm if it fails.
More constructions of hadamard matrices may come. Others may be pure data.
Other may be recursive constructions on both.
> BTW, fmpz_mat_hadamard succeeds for every multiple of 4 below 92;
current code for the Paley construction in Sage doesn't succeed to
construct a size 20 Hadamard matrix.
Then there must be another bug somewhere. This code clearly needs some
testing.
Nathann
--
Ticket URL: <http://trac.sagemath.org/ticket/19340#comment:9>
Sage <http://www.sagemath.org>
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