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Bug #1191

ApproxSolve: log(0) on some examples

Added by John Abbott 27 days ago. Updated 27 days ago.

Status:
Feedback
Priority:
High
Assignee:
Category:
bug
Target version:
Start date:
19 Jun 2018
Due date:
% Done:

90%

Estimated time:
Spent time:

Description

The following input attempts to compute log(0).

use QQ[x,y,z];
L := [y^3 +x*z^2,  2*x^2*y -4*x*z^2 +3*x*y,  2*x^3 +x^2*y -2*z^3]; -- zero dim!
ApproxSolve(L);

History

#1 Updated by John Abbott 27 days ago

  • Status changed from New to In Progress
  • % Done changed from 0 to 10

Something odd must have happened: ApproxSolve is failing on almost trivial examples.
Here are some simpler failing examples:

ideal(-2*x*y^2 +2*x^2 +3*x*y,  -3*y^3 -2*x^2);

ideal(-x^2 +3*x*y -y,  -3*y^2 +x)

Maybe there is a problem when (0,0) is a solution?

#2 Updated by John Abbott 27 days ago

It even fails in a univariate case... -3*x^2+2*x.
Investigating...

#3 Updated by John Abbott 27 days ago

Here is a surprise:

RealRoots(x); --> gives error log(0)

Ulrich has the version from Jan 2018, and his works...
So I must have made a recent change... sigh!

#4 Updated by John Abbott 27 days ago

  • Status changed from In Progress to Feedback
  • Assignee set to John Abbott
  • % Done changed from 10 to 90

The problem was caused by a new better impl of RootBound which can return zero (if arg is just x); the old RootBound could not do this.

Fixed.

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