Opened 8 years ago
Closed 8 years ago
#16224 closed defect (fixed)
incorrect translation of Bessel from Maxima?
Reported by:  kcrisman  Owned by:  

Priority:  major  Milestone:  sage6.3 
Component:  calculus  Keywords:  
Cc:  Merged in:  
Authors:  Nils Bruin  Reviewers:  Peter Bruin 
Report Upstream:  N/A  Work issues:  
Branch:  dd3786f (Commits, GitHub, GitLab)  Commit:  dd3786ff9aa822efb8a5eebbc3fbee2e4c1d55fe 
Dependencies:  Stopgaps: 
Description (last modified by )
From this sagesupport thread:
But other sums are simply wrong. k = var('k') sum(x^(2*k)/factorial(2*k),k,0,oo) gives 1/4*sqrt(2)*sqrt(pi)*x^(3/2) but the answer should be sinh(x). Hmm. That shouldn't be happening, though I wouldn't be surprised if it didn't turn out as easy as that. (%i1) load(simplify_sum); (%o1) /Users/.../Sage5.12OSX64bit10.6.app/Contents/Reso\ urces/sage/local/share/maxima/5.29.1/share/solve_rec/simplify_sum.mac (%i3) display2d:false; (%o3) false (%i4) simplify_sum(sum(x^(2*k)/factorial(2*k),k,0,inf)); (%o4) sqrt(%pi)*bessel_i(1/2,x)*sqrt(x)/sqrt(2) So I'm not sure why that would happen  maybe because of incorrect Bessel simplification? sage: maxima_calculus('bessel_i(1/2,x)') bessel_i(1/2,x) sage: _._sage_() sqrt(2)*sqrt(1/(pi*x))*cosh(x) That gives cosh(x), which I think is what you meant.
I don't know why this would happen, but presumably it should be possible to track down without too much effort.
Change History (11)
comment:1 Changed 8 years ago by
 Description modified (diff)
comment:2 Changed 8 years ago by
comment:3 Changed 8 years ago by
 Branch set to u/nbruin/ticket/16224
 Created changed from 04/24/14 01:37:35 to 04/24/14 01:37:35
 Modified changed from 04/24/14 03:12:12 to 04/24/14 03:12:12
comment:4 Changed 8 years ago by
 Commit set to 303a30b85353abde0e5e9f3d1b1ec0ae31b7b71e
 Status changed from new to needs_review
OK, this should do the trick. I've also made the routines produce an error rather than corrupt the dictionaries. That should make diagnosing such problems a little easier in the future.
If someone wants to add a doctest for this somewhere, go ahead.
New commits:
303a30b  trac 16224: make sure maxima_lib knows about bessel functions.

comment:5 Changed 8 years ago by
On second thought we can probably do better than having to register all this in two spots:sage:
sage: bessel_I._maxima_() bessel_i sage: tbl=sage.symbolic.pynac.symbol_table['maxima'] sage: tbl['bessel_i'] bessel_I
so the information is there already. We should just let sr_to_max
and max_to_sr
look in those spots before reverting to just converting strings back and forth and trying to guess the appropriate symbols from that. That would provide an extra level and would mean that functions like bessel_I
that are spelled differently in maxima
and/or get rewritten can be converted without entering their translations in another spot.
comment:6 followup: ↓ 7 Changed 8 years ago by
 Commit changed from 303a30b85353abde0e5e9f3d1b1ec0ae31b7b71e to b7f21d58b3a5bd58254e659e67aa947e166b5fd3
Branch pushed to git repo; I updated commit sha1. New commits:
b7f21d5  trac 16224: make max_to_sr look in sage.symbolic.pynac.symbol_table['maxima']

comment:7 in reply to: ↑ 6 Changed 8 years ago by
Replying to git:
Branch pushed to git repo; I updated commit sha1. New commits:
b7f21d5 trac 16224: make max_to_sr look in sage.symbolic.pynac.symbol_table['maxima']
This should do a much more programmatic and hence more reliable job than forcing people to register the same information in yet another spot.
comment:8 Changed 8 years ago by
 Milestone changed from sage6.2 to sage6.3
comment:9 Changed 8 years ago by
 Branch changed from u/nbruin/ticket/16224 to u/pbruin/16224maxima_to_sage
 Commit changed from b7f21d58b3a5bd58254e659e67aa947e166b5fd3 to dd3786ff9aa822efb8a5eebbc3fbee2e4c1d55fe
 Reviewers set to Peter Bruin
 Status changed from needs_review to positive_review
comment:10 Changed 8 years ago by
Thanks for both of your work!
comment:11 Changed 8 years ago by
 Branch changed from u/pbruin/16224maxima_to_sage to dd3786ff9aa822efb8a5eebbc3fbee2e4c1d55fe
 Resolution set to fixed
 Status changed from positive_review to closed
It's a problem in the automatic translation learning for
max_to_sr
. If we force it to learn about Bessel functions beforehand, there's no problem:On the other hand, in a fresh session:
The problem is that the
bessel_I(1/2,x)
gets immediately rewritten to another expression, so the default heuristics formax_to_sr
fail. The remedy: initialize the translation of%BESSEL_I
. This consists simply of adding the lineto sage_op_dict in sage/interfaces/maxima_lib.py