Opened 4 years ago

Closed 3 years ago

#17793 closed defect (wontfix)

wrong piecewise convolution

Reported by: rws Owned by:
Priority: minor Milestone: sage-duplicate/invalid/wontfix
Component: symbolics Keywords:
Cc: wdj, kcrisman, jondo, vbraun, slelievre, mkoeppe, eviatarbach, rws Merged in:
Authors: Reviewers:
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

Description (last modified by mkoeppe)

This doctest tests against a wrong result, the resulting curve must have a quadratic part:

            sage: f = piecewise([[(-1,1),1]])                             ## example 2
            sage: g = piecewise([[(0,3),x]])
            sage: f.convolution(g)
            Piecewise defined function with 3 parts, [[(-1, 1), 0], [(1, 2), -3/2*x], [(2, 4), -3/2*x]]

From numerical investigation it seems the solution would be piecewise(x|-->1/2*x^2 + x + 1/2 on (-1/2, 1), x|-->2*x on (1, 2), x|-->-1/2*x^2 + x + 4 on (2, 7/2); x).

This works in the new piecewise from #14801.

The ticket is for documentary reasons because a new piecewise code is being worked on in #14801.

Change History (6)

comment:1 Changed 4 years ago by kcrisman

See also #12123 (possibly the same?) Actually, the fix should be pretty easy once one understands the code, but I gave up here.

comment:2 Changed 4 years ago by rws

  • Description modified (diff)

comment:3 Changed 3 years ago by mkoeppe

  • Cc wdj kcrisman jondo vbraun slelievre mkoeppe eviatarbach rws added
  • Description modified (diff)
  • Milestone changed from sage-6.5 to sage-duplicate/invalid/wontfix
  • Priority changed from major to minor

Works in the new piecewise from #14801. Dup of #12123, which is why I'm setting this to "dup/needs review"

comment:4 Changed 3 years ago by rws

  • Status changed from new to needs_review

comment:5 Changed 3 years ago by rws

  • Status changed from needs_review to positive_review

comment:6 Changed 3 years ago by embray

  • Resolution set to wontfix
  • Status changed from positive_review to closed

Determined to be invalid/duplicate/wontfix (closing as "wontfix" as a catch-all resolution).

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