#28413 closed enhancement (fixed)
Add .h_star_vector to compact rational polytopes
Reported by:  jipilab  Owned by:  

Priority:  major  Milestone:  sage9.1 
Component:  geometry  Keywords:  polytopes, normaliz 
Cc:  selia, chapoton, Winfried, vdelecroix, mkoeppe  Merged in:  
Authors:  Sophia Elia  Reviewers:  JeanPhilippe Labbé 
Report Upstream:  N/A  Work issues:  
Branch:  48d2a6f (Commits, GitHub, GitLab)  Commit:  48d2a6f740428ae4b4c5dc9d431fa73976bd0687 
Dependencies:  #28247  Stopgaps: 
Description
Since #25091 is merged, we can compute a few more things with normaliz. One important object is the socalled h^*
vector, see https://en.wikipedia.org/wiki/Ehrhart_polynomial#Ehrhart_series for details.
This ticket implements this method. Currently, one has to do the following:
sage: C = polytopes.hypercube(3, backend="normaliz") sage: C.ehrhart_series().numerator().coefficients() [1, 23, 23, 1]
which would now become:
sage: C.h_star_vector()
and return an error if the backend is not 'normaliz'
...
See the related SageAsk? question: https://ask.sagemath.org/question/32505/cansagecomputethehvectorofapolytope/
Eventually, it would be nice to also make this possible for polymake too (it would be interesting to know if they use 'normaliz'
for that).
Change History (23)
comment:1 followup: ↓ 2 Changed 2 years ago by
comment:2 in reply to: ↑ 1 Changed 2 years ago by
Replying to ghwbruns:
For the h^{*}vector o be welldefined, the polytope should have integral vertices. Otherwise there is no canonical choice for the denominator and, hence, the numerator of the Ehrhart series (as a rational function).
At least one should check that the denominator is a power of 1t.
Okay! great, good to know. We'll put this check into the function.
comment:3 Changed 23 months ago by
 Branch set to public/28413
 Commit set to 8606b7e70f94b1c0abbd7af5350ba38d7b17e88a
New commits:
8606b7e  first changes for hstar function

comment:4 Changed 23 months ago by
A few comments:
+  ``self``  A lattice polytope with ``backend`` = 'normaliz'.
I would put the backend comment in a NOTE environment, although I am not completely sure. It would be to be checked in the guidelines.
Just a suggestion:
 The h*vector as a list. + A list whose entries give the h*vector.
simplicies
>simplices
In the examples, you are only testing one of the 4 and not the four of them.
The method _h_star_vector_normaliz(self)
in base should return a TypeError
(as the volume_normaliz for example) and the function in backend_normaliz should be appended with _normaliz
.
I would also add a less trivial example, like the 0,1 cube and perhaps hypersimplex? This would be good to get sanity checks. Further, I would include an example that uses a different backend to show even further that it requires normaliz...
Otherwise, looks good!
comment:5 Changed 18 months ago by
 Commit changed from 8606b7e70f94b1c0abbd7af5350ba38d7b17e88a to b9df5455594bf14929f7e7eb32ac12373048431a
Branch pushed to git repo; I updated commit sha1. New commits:
b9df545  addressing comments

comment:6 Changed 18 months ago by
 Dependencies set to #28247
comment:7 Changed 18 months ago by
 Status changed from new to needs_review
comment:8 Changed 18 months ago by
comment:9 Changed 18 months ago by
 Reviewers set to JeanPhilippe Labbé
 Status changed from needs_review to needs_work
It seems there is a merge conflict... Rebase?
In the h_star_vector
function, I would not say
+  ``self``  A lattice polytope with ``backend`` = 'normaliz'.
but use a NOTE to say that the backend should be normaliz.
Once we have the ticket #28880 and followup related to double description in normaliz, it will be possible to ignore the backend and simply obtain the relevant information in order to obtain the h_star_vector using normaliz.
The syntax for math printing should be corrected in:
+ The h*vector of a unimodular simplex S (a simplex with  volume = $\frac{1}{dim(S)!} ) is always 1. Here we test this on  simplicies up to dimension 4: + volume = `\frac{1}{(\dim S)!}`) is always 1. Here we test this on + simplices up to dimension 4::
Only one of the simplices is tested below:
+ sage: s1 = polytopes.simplex(1,backend = 'normaliz')
+ sage: s2 = polytopes.simplex(2,backend = 'normaliz')
+ sage: s3 = polytopes.simplex(3,backend = 'normaliz')
+ sage: s4 = polytopes.simplex(4,backend = 'normaliz')
+ sage: s3.h_star_vector()
+ [1]
Why not something like:
sage: [polytopes.simplex(i,backend='normaliz').h_star_vector() for i in [1,2,3,4]] sage: [[1], [1], [1], [1]]
The function _h_star_vector
in backend_normaliz.py
should be renamed _h_star_vector_normaliz
and the function _h_star_vector_normaliz
in base.py
should return raise TypeError("the backend should be normaliz")
.
I would also add some more examples that involve known examples where values can be relevant to check the validity.
comment:10 Changed 18 months ago by
I addressed many of these comments in the commit b9df545.
comment:11 Changed 18 months ago by
I see. Great!
I only looked at the first commit and started writing. Since there's a merge conflict, I couldn't see the final product.
Ok, so now it would need a rebase in any case.
comment:12 Changed 18 months ago by
 Branch changed from public/28413 to public/28413rebase
 Commit changed from b9df5455594bf14929f7e7eb32ac12373048431a to 73973be3a3896e60448cb02a63e9b0ed9a990cab
comment:13 Changed 18 months ago by
 Commit changed from 73973be3a3896e60448cb02a63e9b0ed9a990cab to ab006dff035943b51b472557b346a966c01cf2a5
Branch pushed to git repo; I updated commit sha1. New commits:
ab006df  removing ehrhart_quasipolynomial

comment:14 Changed 18 months ago by
You should also add a line in the tutorials to link to this function.
comment:15 Changed 18 months ago by
 Milestone changed from sagepending to sage9.1
comment:16 Changed 18 months ago by
 Commit changed from ab006dff035943b51b472557b346a966c01cf2a5 to a7f14cecab3d5c4c12f1aa235b65b140b4b1152c
comment:17 Changed 18 months ago by
 Status changed from needs_work to needs_review
comment:18 Changed 17 months ago by
 Status changed from needs_review to needs_work
 There are no doctests in the function
_h_star_vector_normaliz
inbackend_normaliz.py
.
 The documentation does not build:
[dochtml] docstring of sage.geometry.polyhedron.base.Polyhedron_base.h_star_vector:22: WARNING: Inline interpreted text or phrase reference startstring without endstring.
this is caused by the missing space:
OUTPUT: The h*vector as a list.  ..NOTE: + .. NOTE: The ``backend`` of ``self`` should be ``'normaliz'``.
I also suggest to remove the two backticks around the word backend in the docstrings as it is not a parameter of the functions.
comment:19 Changed 17 months ago by
 Commit changed from a7f14cecab3d5c4c12f1aa235b65b140b4b1152c to 8b8d53d9dcd8baaf194d2d5e6c8e5e45249c6830
Branch pushed to git repo; I updated commit sha1. New commits:
8b8d53d  added tests to backend_normaliz and fixed other comments

comment:20 Changed 17 months ago by
 Status changed from needs_work to needs_review
comment:21 Changed 17 months ago by
 Commit changed from 8b8d53d9dcd8baaf194d2d5e6c8e5e45249c6830 to 48d2a6f740428ae4b4c5dc9d431fa73976bd0687
Branch pushed to git repo; I updated commit sha1. New commits:
48d2a6f  fix documentation

comment:22 Changed 17 months ago by
 Status changed from needs_review to positive_review
Looks good to me now. Tests are passing and the documentation now seems to builds too.
comment:23 Changed 17 months ago by
 Branch changed from public/28413rebase to 48d2a6f740428ae4b4c5dc9d431fa73976bd0687
 Resolution set to fixed
 Status changed from positive_review to closed
For the h^{*}vector o be welldefined, the polytope should have integral vertices. Otherwise there is no canonical choice for the denominator and, hence, the numerator of the Ehrhart series (as a rational function).
At least one should check that the denominator is a power of 1t.