Opened 7 years ago
Closed 6 years ago
#14402 closed enhancement (fixed)
Implement tensor product of infinite crystals
Reported by: | tscrim | Owned by: | sage-combinat |
---|---|---|---|
Priority: | major | Milestone: | sage-5.11 |
Component: | combinatorics | Keywords: | infinite crystals, tensor product |
Cc: | sage-combinat, aschilling, bsalisbury1 | Merged in: | sage-5.11.beta0 |
Authors: | Ben Salisbury, Travis Scrimshaw | Reviewers: | Anne Schilling |
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | #14454, #14266 | Stopgaps: |
Description (last modified by )
Currently tensor product of infinite crystals does not work well, likely due to assumptions that the crystals are finite. This implements a new tensor product of crystals class for handling infinite crystals.
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Attachments (1)
Change History (11)
comment:1 Changed 7 years ago by
- Dependencies set to #14454
comment:2 follow-up: ↓ 3 Changed 7 years ago by
- Milestone changed from sage-5.9 to sage-5.10
- Status changed from new to needs_review
comment:3 in reply to: ↑ 2 Changed 7 years ago by
comment:4 follow-up: ↓ 5 Changed 7 years ago by
- Dependencies changed from #14454 to #14454 #14266
- Description modified (diff)
Hey Anne,
Here's a new version of the patch which changes the computation of epsilon
and phi
and caches in the parent _sig
. I also added a note on the global option on convention to TensorProductOfCrystals
.
I've added documentation about the signature rule, but this does not apply for non-regular crystals. For example, consider the highest weight element in B infinity tensored with itself. Both phi_i
and epsilon_i
are 0 for all i
, so by the signature rule, this would be 0
for f_i
which is not the case.
For the previous implementation, did you mean the old TensorProductOfCrystalsElement
? If so, then it assumed the signature rule gave the crystal structure, which is why it didn't work. I didn't want to put this into the doc since it's an implementation detail, but if you think it should be, then we can add it in.
Also the dependency on #14266 is trivial due to a change of sources.py
, and this can easily be commuted past.
Thank you for doing the review,
Travis
comment:5 in reply to: ↑ 4 Changed 6 years ago by
Hi Travis,
I left a review patch on the sage-combinat queue. In particular, I think the formula for \phi_i in terms of the a_i was not quite right in your patch, so I tried to correct it (it is now very simple, namely max(\lambda_i+a_i(k))). Please check that you agree! I also changed the code accordingly. The tests still pass. Since the change did not seem to make a difference for the tests, it might be a good idea to put some stronger tests in that check all possible cases for the \epsilon_i and \phi_i, so that you are sure that the code is doing what it is supposed to be doing (perhaps run some exhaustive tests for regular crystals in some example against the alternative implementation).
If you are happy with the review patch you can fold it in and make the above changes as well.
Thanks!
Anne
Changed 6 years ago by
comment:6 Changed 6 years ago by
Hey Anne,
The reason why tests didn't break is because it is equivalent. To see this, note that
a_i(k+1) = a_i(k) + \epsilon_i(b_{k+1}) - \phi_i(b_k)
which is how _sig()
is recursively computed. However this way is much more clear and clean. I've uploaded the folded patch and pushed to the queue.
Best,
Travis
For patchbot:
Apply: trac_14402-tensor_product_infinite_crystals-ts.patch
comment:7 Changed 6 years ago by
- Reviewers set to Anne Schilling
- Status changed from needs_review to positive_review
comment:8 Changed 6 years ago by
- Dependencies changed from #14454 #14266 to #14454, #14266
- Milestone changed from sage-5.10 to sage-5.11
comment:9 Changed 6 years ago by
Hey Anne,
Thank you for doing the review.
Best,
Travis
comment:10 Changed 6 years ago by
- Merged in set to sage-5.11.beta0
- Resolution set to fixed
- Status changed from positive_review to closed
Hi Ben and Travis,
Thanks for your work on this! Here are some initial comments:
You are computing the partial sums over and over. Why not something like
and similarly for phi. You could also optimize the computation of a_i(k) (which I guess is in _sig) and then use the formula of epsilon in terms of a_i(k).
So much for now.
Anne