Opened 4 years ago
Closed 4 years ago
#21263 closed enhancement (fixed)
Poset: additions to is_eulerian()
Reported by:  jmantysalo  Owned by:  

Priority:  major  Milestone:  sage7.4 
Component:  combinatorics  Keywords:  
Cc:  Merged in:  
Authors:  Jori Mäntysalo  Reviewers:  Frédéric Chapoton 
Report Upstream:  N/A  Work issues:  
Branch:  8eb5cc3 (Commits)  Commit:  8eb5cc3aba871a6481e77ac27e0428a39e09edd6 
Dependencies:  Stopgaps: 
Description
This patch will 1) slightly speed up computing is_eulerian()
, 2) make it possible to check if a poset is (only) keulerian for some integer k, 3) get a "certificate" of noneulerianity, i.e. endpoints of a noneulerian interval and 4) add star_product()
. The last logically belongs to this IMO, as it is mostly used for generating a new Eulerian poset.
It is logically possible to define this for P
and Q
if P
has top and Q
has bottom. However, this implementation requires both to have both bottom and top. On the other hand this does not check if a poset is graded.
Change History (12)
comment:1 Changed 4 years ago by
 Branch set to u/jmantysalo/keulerian
comment:2 Changed 4 years ago by
 Commit set to b92aa699f4f8709ca37fcb587f3e5b4591f5a9f8
 Status changed from new to needs_review
comment:3 followup: ↓ 5 Changed 4 years ago by
in star, missing doctests for the raise statements.
comment:4 Changed 4 years ago by
 Commit changed from b92aa699f4f8709ca37fcb587f3e5b4591f5a9f8 to 6ec10fd511e5935ae763db60b5bd587a44df51c5
Branch pushed to git repo; I updated commit sha1. New commits:
6ec10fd  Add tests for input checking.

comment:5 in reply to: ↑ 3 Changed 4 years ago by
comment:6 followup: ↓ 8 Changed 4 years ago by
There are some "eulerian" that should take a capital.
Do you have a reference for testing only even ranks differences ?
comment:7 Changed 4 years ago by
 Commit changed from 6ec10fd511e5935ae763db60b5bd587a44df51c5 to 1e73455de646964b5f4a45ec46120712c7f543bd
Branch pushed to git repo; I updated commit sha1. New commits:
1e73455  Capital letter in 'eulerian'.

comment:8 in reply to: ↑ 6 Changed 4 years ago by
Replying to chapoton:
There are some "eulerian" that should take a capital.
Those corrected. I don't know if I should write "kEulerian" or "keulerian"; Volker said that english is not consistent on that.
Do you have a reference for testing only even ranks differences ?
For example EC in pages 453454 exercise 174c indirectly says that. For a paper see abstract of http://www.ms.uky.edu/~jrge/Papers/kEulerian.pdf
comment:9 followup: ↓ 11 Changed 4 years ago by
 Reviewers set to Frédéric Chapoton
ok, looks good. Please add a reference to the Ehrenborg article, and then you can set to positive.
comment:10 Changed 4 years ago by
 Commit changed from 1e73455de646964b5f4a45ec46120712c7f543bd to 8eb5cc3aba871a6481e77ac27e0428a39e09edd6
Branch pushed to git repo; I updated commit sha1. New commits:
8eb5cc3  Added reference for optimization.

comment:11 in reply to: ↑ 9 Changed 4 years ago by
 Status changed from needs_review to positive_review
Replying to chapoton:
ok, looks good. Please add a reference to the Ehrenborg article, and then you can set to positive.
Done that.
comment:12 Changed 4 years ago by
 Branch changed from u/jmantysalo/keulerian to 8eb5cc3aba871a6481e77ac27e0428a39e09edd6
 Resolution set to fixed
 Status changed from positive_review to closed
New commits:
Add star_product etc.