#7301: Gale Ryser theorem
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   Reporter:  ncohen         |       Owner:  mhansen     
       Type:  enhancement    |      Status:  needs_review
   Priority:  major          |   Milestone:  sage-4.3.1  
  Component:  combinatorics  |    Keywords:              
Work_issues:                 |      Author:              
   Upstream:  N/A            |    Reviewer:              
     Merged:                 |  
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Comment(by wdj):

 In reply to an email Nathann Cohen sent me:

 > Several questions about your patch :
 >    * Do you think function slider01 is useful by itself in the
 > integer_vector class ( and if so, under, should'nt it be renamed to be
 > more "explicit", if possible ? ) ? My advice is that it may be better
 > to move it *inside* of function fale_ryser_theorem


 Python has a mechanism for "private" functions like slider01, so
 I renamed it _slider01. I think that is better than hiding it inside
 gale_ryser_theorem. Is that okay?


 >    * There is one commented line in is_gale_ryser
 >    * Why don't you want to use the method Partition.dominates for
 > your test in is_gale_ryser ?


 I think this will not work, if you want to allow trailing 0's.
 Maybe I am missing something?


 >    * Why do you say that the LP formulation is Gale's construction ?
 > You mean that Gale proved this result using LinearProgramming ? If so,
 > do you have access to an electronic version of the text you are citing
 > ? I'd be extremely interested in giving it a look... Very few
 > theretical results are proved using LP :-)

 I was told that by my colleague which is much much more of an expert on
 this stuff. I have not read Gale's paper and don't know of an electronic
 version.


 >    * In you docstrings you frequently use $$ for LaTeX expressions.
 > As I never saw it anywhere in Sphinx, I do not know whether it works :
 > I always use ` instead of $. Is the documentation built correctly this
 > way ? I prefer your $ to my usual `, so I'm interested in the
 > answer....


 I changed all $ to '. Thanks!


 >    * I will be running tests to compare the speed of your
 > construction of the matrices... I expect your method to be much faster
 > than mine, perhaps something about it should be said in the docstrings
 >    * I do not know if it is a requirement of Sphinx, but Minh ( who I
 > claim is perfection made flesh ) gave me several "needs work" because
 > of the way I formatted docstrings for References. What I take for
 > model now is the functions citing Cliquer in the graph.py file. The
 > document's keys are not integers but "the usual" concatenations of the
 > authors'initials and the year, for example [Ryser63] and [Gale57].
 > Besides, they appear with a trailing _ when used to cite the paper.
 > You are bound to find one if you look for the string "]_" in Sage's
 > files ( but you will definitely find them if you look for "Cliquer" in
 > sage/graphs/graph.py"


 Thank you for the reference! I think the docstrings are okay now.


 >    * In gale_ryser_theorem the two :: after EXAMPLES should be
 > removed for the generated documentation to be correct. Same thing
 > after References, and in slider01. The sign :: is saying to Sphinx
 > that what is following is a piece of Sage code. So you should only
 > write them when it is the case, for example after EXAMPLES in
 > is_gale_ryser. It may be better to generate the documentation to check
 > that it is visually correct :-)


 Done. Thanks.


 >
 > I will be keeping an eye on Sage-devel to be kept aware of the next
 > alpha release... I tried alpha0 which failed to compile on my computer
 > and I am at the moment without any Sage install available ( I have
 > sage.math in case of need, though ). I hope it will be available soon
 > :-))))))

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7301#comment:29>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
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