Opened 7 years ago
Closed 5 years ago
#18386 closed defect (fixed)
Doctests for: fix polylog evalf
Reported by:  rws  Owned by:  

Priority:  major  Milestone:  sage8.1 
Component:  symbolics  Keywords:  pynac special 
Cc:  fbissey  Merged in:  
Authors:  Ralf Stephan  Reviewers:  Paul Masson, Dima Pasechnik 
Report Upstream:  N/A  Work issues:  
Branch:  59d4b29 (Commits, GitHub, GitLab)  Commit:  59d4b29e5e417a12c9f5cf1bdc58c1fdd810da42 
Dependencies:  #22969, #23077, #23134  Stopgaps: 
Description (last modified by )
The polylog
function (from Pynac) treats 1.0
like 1
and does not immediately evalf
with some numeric arguments.
sage: polylog(2,1) 1/6*pi^2 sage: polylog(2.,1) 1.64493406684823 sage: polylog(2,1.0) 1/6*pi^2 sage: polylog(2,0.9) polylog(2, 0.900000000000000) sage: _.n() TypeError: cannot evaluate symbolic expression numerically
What makes polylog
different is that the Sage polylog
has no special value logic and calls Pynac's Li_eval
for everything. This handles special values (incorrectly if an arg is FP) and sends everything else back with .hold()
. So you need N()
to get FP results that are not special. With FP Pynac is called which then calls Sage/mpmath. But this then bombs with FP args.
Change History (30)
comment:1 Changed 7 years ago by
 Description modified (diff)
 Report Upstream changed from N/A to Reported upstream. Developers acknowledge bug.
comment:2 Changed 7 years ago by
 Description modified (diff)
 Milestone changed from sage6.7 to sage6.8
 Summary changed from polylog quirks to implement polylog completely in Sage
comment:3 Changed 6 years ago by
 Description modified (diff)
 Milestone changed from sage6.8 to sage7.3
 Summary changed from implement polylog completely in Sage to fix polylog evalf
comment:4 Changed 6 years ago by
 Report Upstream changed from Reported upstream. Developers acknowledge bug. to Fixed upstream, in a later stable release.
comment:5 Changed 6 years ago by
 Dependencies set to #21034
 Reviewers set to Paul Masson
 Status changed from new to needs_review
comment:6 followup: ↓ 8 Changed 6 years ago by
 Milestone changed from sage7.3 to sage7.4
 Status changed from needs_review to needs_work
comment:7 Changed 6 years ago by
Polylog has a branch point/discontinuity at arguments (2,1). Anyway, we're just taking what arb is giving us:
sage: RBF=ComplexBallField(53) sage: RBF(1.5).polylog(RBF(2.5)) [2.27833425640 +/ 2.25e12] + [0.61016023975 +/ 3.09e12]*I sage: RBF(.99999999).polylog(RBF(2.)) [1.6449338726414 +/ 9.23e14] + [+/ 2.46e13]*I sage: RBF(1.).polylog(RBF(2.)) nan + nan*I sage: RBF(1.00000001).polylog(RBF(2.)) [1.644934261055 +/ 1.08e13] + [3.1416e8 +/ 3.19e13]*I sage: polylog(2,1) 1/6*pi^2
This is very sensible because if you need the exact value say so, and if you need an inexact value to 53 (or any) digits the result cannot be given in that precision so it's NaN. I'll concede that, similar to #19439 it may be desired to return the symbolic NaN.
comment:8 in reply to: ↑ 6 Changed 6 years ago by
 Milestone changed from sage7.4 to sageduplicate/invalid/wontfix
 Status changed from needs_work to needs_review
Replying to paulmasson:
I'm finding this behavior odd:
sage: polylog(2,1.) NaN  NaN*IThis doesn't look fixed upstream to me:
evalf
needs to return a numeric value.
Evalf does return a numeric value, too:
sage: polylog(2,1.0).n() NaN  NaN*I sage: type(_) <type 'sage.rings.complex_number.ComplexNumber'>
so, together with my previous answer I think this ticket can be closed.
comment:9 Changed 5 years ago by
 Milestone changed from sageduplicate/invalid/wontfix to sage8.0
 Status changed from needs_review to needs_work
That was badly mistyped and misinterpreted by me, so back to the issue.
comment:10 Changed 5 years ago by
Note also
sage: polylog(3,RBF(1.1)) # there is a polylog RBF member! 1.37625299668538  0.0142691615444952*I sage: dilog(RBF(1.1)) 1.96199910130557  0.299425760685590*I
comment:11 Changed 5 years ago by
 Branch set to u/rws/fix_polylog_evalf
comment:12 Changed 5 years ago by
 Branch changed from u/rws/fix_polylog_evalf to u/rws/183861
comment:13 Changed 5 years ago by
 Commit set to 5e182f34798ac3d092aa3e85e5b2fdac4226ce7a
 Dependencies changed from #21034 to pynac0.7.7
comment:14 Changed 5 years ago by
 Branch changed from u/rws/183861 to u/rws/183862
comment:15 Changed 5 years ago by
 Commit changed from 5e182f34798ac3d092aa3e85e5b2fdac4226ce7a to 51aeae38a87d568034d69a310b680c50146179da
 Dependencies changed from pynac0.7.7 to #22969
 Status changed from needs_work to needs_review
New commits:
51aeae3  18386: doctest dilog/polylog fixes

comment:16 Changed 5 years ago by
 Status changed from needs_review to needs_work
Fails tests with reduced precision.
comment:17 Changed 5 years ago by
 Commit changed from 51aeae38a87d568034d69a310b680c50146179da to 074034a15c082ede5641bd73d4b1a6cb9dfefb9c
Branch pushed to git repo; I updated commit sha1. New commits:
074034a  Merge branch 'develop' into t/18386/183862

comment:18 Changed 5 years ago by
 Report Upstream changed from Fixed upstream, in a later stable release. to Not yet reported upstream; Will do shortly.
comment:19 Changed 5 years ago by
 Dependencies changed from #22969 to #22969, #23077, pynac0.7.8
We depend on #23077 and pynac0.7.8 for improved handling of complex floats.
comment:20 Changed 5 years ago by
 Dependencies changed from #22969, #23077, pynac0.7.8 to #22969, #23077, #23134
 Report Upstream changed from Not yet reported upstream; Will do shortly. to N/A
comment:21 Changed 5 years ago by
 Status changed from needs_work to needs_review
 Summary changed from fix polylog evalf to Doctests for: fix polylog evalf
Now that all dependencies are merged, let the patchbots test it and please review.
comment:22 Changed 5 years ago by
See #23565 for some changes to the behavior of polylog. Are those changes improvements?
comment:23 followup: ↓ 25 Changed 5 years ago by
The biggest mystery here to me is how pynac is being able to use arb...
comment:24 Changed 5 years ago by
 Dependencies changed from #22969, #23077, #23134 to #22969, #23077, #23134, #23565
 Milestone changed from sage8.0 to sageduplicate/invalid/wontfix
 Reviewers changed from Paul Masson to Paul Masson, Dima Pasechnik
 Status changed from needs_review to positive_review
the doctests added here, with correct (no NaN
s!) outputs, are being added to #23565
comment:25 in reply to: ↑ 23 ; followup: ↓ 26 Changed 5 years ago by
Replying to dimpase:
The biggest mystery here to me is how pynac is being able to use arb...
Pynac calls Sage's arb interface via the Python C API.
comment:26 in reply to: ↑ 25 Changed 5 years ago by
 Cc fbissey added
comment:27 Changed 5 years ago by
 Dependencies changed from #22969, #23077, #23134, #23565 to #22969, #23077, #23134
comment:28 Changed 5 years ago by
 Branch changed from u/rws/183862 to u/fbissey/183862
 Commit changed from 074034a15c082ede5641bd73d4b1a6cb9dfefb9c to 59d4b29e5e417a12c9f5cf1bdc58c1fdd810da42
comment:29 Changed 5 years ago by
 Milestone changed from sageduplicate/invalid/wontfix to sage8.1
comment:30 Changed 5 years ago by
 Branch changed from u/fbissey/183862 to 59d4b29e5e417a12c9f5cf1bdc58c1fdd810da42
 Resolution set to fixed
 Status changed from positive_review to closed
Ralf, there was a typo in the description of #21034 pointing to #18368 rather than this ticket.
I'm finding this behavior odd:
This doesn't look fixed upstream to me:
evalf
needs to return a numeric value.The doctest in
functions/log.py
captures the current behavior, but needs to be updated before this ticket can be closed.