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Bug #1484

ker bug (quotientinghom for R/ideal())

Added by John Abbott over 3 years ago. Updated over 2 years ago.

Status:
Closed
Priority:
Normal
Assignee:
Anna Maria Bigatti
Category:
Maths Bugs
Target version:
CoCoALib-0.99800
Start date:
14 Sep 2020
Due date:
% Done:

100%

Estimated time:
2.52 h
Spent time:
2.55 h

Description

Bernhard Andraschko reports the following bug:

/**/ R ::= QQ[x,y,z];
/**/ I := ideal(R,[]);
/**/ S := R/I;
/**/ phi := QuotientingHom(S);
/**/ ker(phi); --> ERROR

Related issues

Related to CoCoALib - Feature #1329: New syntax for creating homomorphisms (PolyAlgebraHom)Closed2019-10-08

Related to CoCoALib - Bug #1571: ker_H needs careNew2021-01-29

History

#1 Updated by John Abbott over 3 years ago

I have blindly changed the code in HomomorphismOps.C.
The problem was in MakeRichHom (and presumably an analogous problem in MakeRichHom_H).
The changes are on lines 167 and 244.

Anna: could you check that what I have done is reasonable? Bernhard's example works OK now.

#2 Updated by John Abbott over 3 years ago

  • Status changed from New to Resolved
  • % Done changed from 0 to 80

There are two more suspect creations of ideals: line 325 and 347.
I have changed these too, but am less sure that what I have done is correct (not even sure how to test my changes). Could you do this, Anna?

#3 Updated by Anna Maria Bigatti over 3 years ago

  • Assignee set to Anna Maria Bigatti

#4 Updated by Anna Maria Bigatti over 3 years ago

For me: test, and add CoCoALib tests

#5 Updated by Anna Maria Bigatti over 3 years ago

Anna! check ring for empty lists!

#6 Updated by Anna Maria Bigatti over 3 years ago

John Abbott wrote:

There are two more suspect creations of ideals: line 325 and 347.
I have changed these too, but am less sure that what I have done is correct (not even sure how to test my changes). Could you do this, Anna?

I confirm the rings are right.
Now I inserted some verbosity to properly check it.

#7 Updated by Anna Maria Bigatti about 3 years ago

For proper testing I added some verbosity, but I cannot see it.

/**/ SetVerbosityLevel(91);
/**/ ker(QuotientingHom(R/ideal(R,[])));
/**/ ker(QuotientingHom(R/ideal(x^2+1)));

what am I missing? investigating...

#8 Updated by Anna Maria Bigatti about 3 years ago

  • Related to Feature #1329: New syntax for creating homomorphisms (PolyAlgebraHom) added

#9 Updated by Anna Maria Bigatti about 3 years ago

Anna Maria Bigatti wrote:

For proper testing I added some verbosity, but I cannot see it.
[...]
what am I missing? investigating...

those were easy cases! ;-)

ker(InducedHom(R/ideal(x-y),PolyAlgebraHom(R,R/ideal(x-y),"x,y,z")));

this works and triggers the verbosity

#10 Updated by Anna Maria Bigatti about 3 years ago

  • Status changed from Resolved to Feedback
  • % Done changed from 80 to 90

#11 Updated by Anna Maria Bigatti about 3 years ago

  • Related to Bug #1571: ker_H needs care added

#12 Updated by John Abbott over 2 years ago

  • Status changed from Feedback to Closed
  • % Done changed from 90 to 100
  • Estimated time set to 2.52 h

Added test to test-exbugs.C.

Closing.

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