Opened 8 months ago
Closed 7 months ago
#15654 closed defect (fixed)
PARI discriminant speed depends on stack size
Reported by: | jdemeyer | Owned by: | |
---|---|---|---|
Priority: | major | Milestone: | sage-6.2 |
Component: | performance | Keywords: | |
Cc: | pbruin | Merged in: | |
Authors: | Jeroen Demeyer | Reviewers: | David Roe |
Report Upstream: | Reported upstream. Developers deny it's a bug. | Work issues: | |
Branch: | u/jdemeyer/ticket/15654 (Commits) | Commit: | a955e45e17cdbd40d24a103ef7903c5f970b24a3 |
Dependencies: | #15653 | Stopgaps: |
Description (last modified by jdemeyer)
This is weird and bad:
sage: x = polygen(ZpFM(3,10)) sage: p = ((x-1)^50 + x)._pari_init_() sage: %time pari(p).poldisc() CPU times: user 52.73 s, sys: 0.00 s, total: 52.73 s Wall time: 52.82 s 2*3 + 3^4 + 2*3^6 + 3^7 + 2*3^8 + 2*3^9 + O(3^10) sage: pari.allocatemem(2<<20) PARI stack size set to 2097152 bytes sage: %time pari(p).poldisc() CPU times: user 0.08 s, sys: 0.00 s, total: 0.08 s Wall time: 0.08 s 2*3 + 3^4 + 2*3^6 + 3^7 + 2*3^8 + 2*3^9 + O(3^10)
Upstream: http://pari.math.u-bordeaux.fr/cgi-bin/bugreport.cgi?bug=1507
Change History (18)
comment:1 Changed 8 months ago by jdemeyer
- Description modified (diff)
comment:2 Changed 8 months ago by jdemeyer
- Description modified (diff)
- Summary changed from Extremely slow PARI discriminants to PARI discriminant speed depends on stack size
comment:3 Changed 8 months ago by jdemeyer
- Description modified (diff)
- Report Upstream changed from N/A to Reported upstream. No feedback yet.
comment:4 Changed 8 months ago by jdemeyer
- Dependencies set to #15653
comment:5 Changed 8 months ago by jdemeyer
- Report Upstream changed from Reported upstream. No feedback yet. to Reported upstream. Developers deny it's a bug.
comment:6 Changed 8 months ago by jdemeyer
- Branch set to u/jdemeyer/ticket/15654
- Created changed from 01/09/14 06:03:17 to 01/09/14 06:03:17
- Modified changed from 01/09/14 08:04:16 to 01/09/14 08:04:16
comment:7 Changed 8 months ago by jdemeyer
- Commit set to a955e45e17cdbd40d24a103ef7903c5f970b24a3
- Status changed from new to needs_review
comment:8 Changed 8 months ago by jdemeyer
This solution works well for Sage, maybe not for PARI/GP upstream.
comment:9 follow-ups: ↓ 10 ↓ 11 ↓ 13 Changed 8 months ago by roed
I'm fine with this change. I'm not yet familiar with reviewing SPKG changes using the new directory layout. Why is SPKG.txt deleted in this commit?
More generally, are there other places in Sage where we should be more aggressive about increasing the Pari stack size? If someone is using Pari nontrivially, our current stack size seems too small. Should we increase the stack whenever a user does certain operations signaling that they're going to be using Pari extensively (e.g. create a number field of degree larger than 4, take the discriminant of a polynomial of large degree...)?
comment:10 in reply to: ↑ 9 Changed 8 months ago by jdemeyer
Replying to roed:
I'm fine with this change. I'm not yet familiar with reviewing SPKG changes using the new directory layout. Why is SPKG.txt deleted in this commit?
Not all of SPKG.txt, just the changelog.
comment:11 in reply to: ↑ 9 Changed 8 months ago by jdemeyer
Replying to roed:
More generally, are there other places in Sage where we should be more aggressive about increasing the Pari stack size? If someone is using Pari nontrivially, our current stack size seems too small. Should we increase the stack whenever a user does certain operations signaling that they're going to be using Pari extensively (e.g. create a number field of degree larger than 4, take the discriminant of a polynomial of large degree...)?
We could detect the problem by adding some code to gerepile...() to count the number of garbage collections. We could for example give a warning if more than N happen per second (for a suitable value of N).
comment:12 Changed 8 months ago by jdemeyer
See #15659.
comment:13 in reply to: ↑ 9 Changed 8 months ago by jdemeyer
comment:14 Changed 8 months ago by roed
Cool. I'm doctesting this ticket and will then give it a positive review.
comment:15 Changed 8 months ago by roed
- Reviewers set to David Roe
- Status changed from needs_review to positive_review
Looks good.
comment:16 Changed 8 months ago by vbraun
- Priority changed from critical to major
Ok, this is not "critical"
comment:17 Changed 7 months ago by vbraun_spam
- Milestone changed from sage-6.1 to sage-6.2
comment:18 Changed 7 months ago by vbraun
- Resolution set to fixed
- Status changed from positive_review to closed
New commits: