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Bug #1101

Bug in MinPolyModular (insufficient rational reconstruction)

Added by Anna Maria Bigatti 6 months ago. Updated 2 months ago.

Status:
Closed
Priority:
High
Category:
Buggy Maths
Target version:
Start date:
11 Sep 2017
Due date:
% Done:

100%

Estimated time:
3.00 h
Spent time:

Description

Rational reconstruction succeeds "too early"

/**/ L:=[3*x^3*y +3*y*z^3 +1,  2*x*y*z^2 +3*x,  2*y^3*z +1];
/**/ I := ideal(L);
/**/ mp := MinPolyQuot(x, I, x);
/**/ mp isin I;
false
/**/ mp;
x^16 +(15/2)*x^10 +(45/4)*x^4 +(-1/2028)*x


Related issues

Related to CoCoA-5 - Bug #1100: PrimaryDecomposition0: says not 0-dim but IsZeroDim says ideal is zero-dim!Closed2017-09-11

History

#1 Updated by Anna Maria Bigatti 6 months ago

  • Project changed from CoCoA-5 to CoCoALib
  • Category changed from enhancing/improving to Buggy Maths
  • Target version changed from CoCoA-5.2.2 to CoCoALib-0.99560
  • % Done changed from 0 to 20

Adding Horner evaluation to check minpoly correct reconstruction.

#2 Updated by Anna Maria Bigatti 6 months ago

  • Related to Bug #1100: PrimaryDecomposition0: says not 0-dim but IsZeroDim says ideal is zero-dim! added

#3 Updated by Anna Maria Bigatti 6 months ago

  • Status changed from New to Resolved
  • Priority changed from Normal to High
  • % Done changed from 20 to 70
  • Estimated time set to 3.00 h

Fixed. I implemented a Horner evaluation in MinPoly.C which may be improved, and maybe moved into some other file (and also exported to cocoa5, so we can delete it from PrimaryDecomposition0.cpkg5).

/**/ L:=[3*x^3*y +3*y*z^3 +1,  2*x*y*z^2 +3*x,  2*y^3*z +1];
/**/ I := ideal(L);
/**/ mp := MinPolyQuot(x, I, x);
/**/ mp isin I;
/**/ /**/ /**/ true
/**/ mp;
x^16 +(15/2)*x^10 +(45/4)*x^4 +(1594195/5184)*x

#4 Updated by John Abbott 6 months ago

Here are some more examples which the computer found during the night:

[3*x*y*z^3 +z^2 +1,  3*y^3*z +z^2,  2*x*y^2*z^2 +3*x*y*z^2]

[x^2*y^2 +3*y^3*z +1,  x*y*z^2 +x*y^2,  2*y^3 +3]

#5 Updated by John Abbott 6 months ago

JAA has added test-MinPoly1.C including the 3 examples listed here.
Checking in now.

#6 Updated by John Abbott 4 months ago

  • Status changed from Resolved to Feedback
  • % Done changed from 70 to 90

#7 Updated by John Abbott 2 months ago

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

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