Opened 4 years ago

Last modified 11 months ago

#18697 new defect

any FP number in an Expression without symbol should trigger evaluation

Reported by: rws Owned by:
Priority: major Milestone: sage-6.8
Component: symbolics Keywords:
Cc: Merged in:
Authors: Reviewers:
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: #10035 Stopgaps:

Description (last modified by rws) 

sage: 0.1 * cos(pi/13)
0.100000000000000*cos(1/13*pi)

This is annoying because the 0.1 at once limits the precision of any other non-symbolic expression.

​https://github.com/pynac/pynac/issues/71

Change History (7)

comment:1 Changed 4 years ago by rws

  • Report Upstream changed from N/A to Reported upstream. Developers acknowledge bug.

comment:2 Changed 4 years ago by rws

  • Dependencies set to #10035

People will complain if they cannot change this behaviour, so we need a hold context.

comment:3 Changed 4 years ago by rws

  • Description modified (diff)

comment:4 Changed 4 years ago by rws

  • Report Upstream changed from Reported upstream. Developers acknowledge bug. to Fixed upstream, but not in a stable release.

comment:5 Changed 4 years ago by rws

  • Description modified (diff)
  • Report Upstream changed from Fixed upstream, but not in a stable release. to N/A

Partial "fix" of Sage code removed, it was actually an unrelated Pynac issue, which is fixed in 0.4.2.

comment:6 follow-up: Changed 18 months ago by rws

The problem with this ticket is shown by 

    sage: pi + RBF(1)

The expected output would be [4.141592653589793 +/- 5.61e-16], i.e. the same as with RBF(pi) + RBF(1). Constant conversions thus need to take the right parent into account. There may be multiple incompatible parents and that fact may be hidden deep in the expression tree.

Last edited 18 months ago by rws (previous) (diff)

comment:7 in reply to: ↑ 6 Changed 11 months ago by rws

Replying to rws:

There may be multiple incompatible parents and that fact may be hidden deep in the expression tree.

This is not a problem because we are evaluating depth-first. The only problem at all seems de-facto limited precision constants, in spite of #18255. Also this might be in the way: ​https://github.com/pynac/pynac/issues/311

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