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Bug #163

RealRootsApprox bombs

Added by John Abbott almost 12 years ago. Updated over 11 years ago.

Status:
Closed
Priority:
Normal
Assignee:
Category:
Incomplete function
Target version:
Start date:
20 May 2012
Due date:
% Done:

100%

Estimated time:
Spent time:

Description

The following lines produce an ERR::SERIOUS on my installation

Use QQ[x];
F := x^8 -x^7 -8*x^6 -6*x^5 -9*x^3 -16*x^2 -8*x -1;
RealRootsApprox(FStar,10^(-10));

This may be related to my experimental blocking of GCDs in fields.

History

#1 Updated by John Abbott almost 12 years ago

The example I gave contains FStar instead of F.

The bug is simply an unwarranted error; JAA does not believe there is any risk of getting a wrong answer.

As I suspected the problem is the computation of GCD between ringelems in QQ. Will continue to investigate.

#2 Updated by John Abbott almost 12 years ago

Added a new C5 test file.

The RealRoots code is rather messy; I suppose it should be rewritten in C++. Any volunteers?

I thought I'd fixed the problem but the code still fails sometimes.

#3 Updated by John Abbott almost 12 years ago

  • Status changed from New to Resolved

I've modified RealRoots, and it seems to work now.

What puzzles me is that the bug came to light only today, even though I've been using RealRoots (on very similar examples) intensively for the last week. I believe the bug was introduced when adapting the code to run in CoCoA-5.

I'll check in the changes I've made, but will wait a little before declaring the issue closed.

#4 Updated by John Abbott almost 12 years ago

  • Status changed from Resolved to Closed
  • Assignee set to John Abbott
  • % Done changed from 0 to 100

I've contined to use RealRootsApprox intensively, and no further problems have come to light. So I'm closing this issue.

#5 Updated by Anna Maria Bigatti over 11 years ago

  • Project changed from CoCoA to CoCoA-5

#6 Updated by Anna Maria Bigatti over 11 years ago

  • Category set to Incomplete function
  • Target version set to CoCoA-5.0.3

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