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Bug #1080

intersect: problem with zero generators

Added by John Abbott about 1 year ago. Updated 7 months ago.

Status:
Closed
Priority:
High
Category:
Incomplete function
Target version:
Start date:
16 Jun 2017
Due date:
% Done:

100%

Estimated time:
1.71 h
Spent time:

Description

There are still problems with zero generators:

use R ::= QQ[x,y];
I1 := ideal(x,zero(R));
I2 := ideal(y);
intersect(I1,I2); --> ERROR

I thought this had been fixed :-(


Related issues

Related to CoCoA-5 - Bug #446: intersection fails with zero idealClosed2014-02-20

History

#1 Updated by John Abbott about 1 year ago

  • Related to Bug #446: intersection fails with zero ideal added

#2 Updated by John Abbott about 1 year ago

The problem appears to be the ctor for a GPoly which does not allow GPoly of 0 to be created.
Location TMPGreductor.C:1563 inside fn EmbedPoly.

Anna, are you able to read Max's code?

#3 Updated by Anna Maria Bigatti about 1 year ago

  • Description updated (diff)
  • Assignee set to Anna Maria Bigatti

#4 Updated by John Abbott about 1 year ago

We must remember to add some tests for various failing cases when this has been resolved.

PS it is a little tedious that CoCoA does not accept ideal(x,0,y) because it wants a RINGELEM instead of an INT; of course, it is no often that one wants to give explicitly an INT as a generator, so perhaps the error message is a "feature"?

#5 Updated by Anna Maria Bigatti 8 months ago

  • Status changed from New to Feedback
  • Estimated time set to 1.01 h

I added the function EmbedPolyListNo0 in TmpGReductor.C.
It does the same as EmbedPolyList but skipping zero polynomials.
This should indeed be used always, instead of EmbedPolyList, but it'd better checked case by case (for example for syzygies one should be careful....)

#6 Updated by Anna Maria Bigatti 8 months ago

  • % Done changed from 0 to 90

#7 Updated by Anna Maria Bigatti 7 months ago

  • Status changed from Feedback to Closed
  • % Done changed from 90 to 100

#8 Updated by Anna Maria Bigatti 7 months ago

  • Estimated time changed from 1.01 h to 1.71 h

added test in exbugs.

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