Project

General

Profile

Bug #956

determinant: fails for 0x0 matrix (SEGV)

Added by John Abbott over 7 years ago. Updated almost 7 years ago.

Status:
Closed
Priority:
Normal
Assignee:
John Abbott
Category:
Maths Bugs
Target version:
CoCoALib-0.99550 spring 2017
Start date:
27 Oct 2016
Due date:
% Done:

100%

Estimated time:
0.51 h
Spent time:
0.50 h

Description

The following triggers a SEGV:

Id0 := IdentityMat(ZZ,0); // works OK
det(Id0);

Related issues

Related to CoCoALib - Feature #11: Bareiss algorithmClosed2011-10-20

History

#1 Updated by John Abbott over 7 years ago

#2 Updated by John Abbott over 7 years ago

  • Status changed from New to Resolved
  • Assignee set to John Abbott
  • % Done changed from 0 to 80

The problem was simply that the generic Bariess code failed (on the very last line) when given a 0x0 matrix.

I have added special case code for 0x0 and 1x1 matrices. Actually I added this code several times: is it right that it should be added so often?

This case is now effectively tested by the new test-MatrixSpecial2.C

#3 Updated by John Abbott over 7 years ago

I am still puzzled about how best to handle the trivial cases (0x0 and 1x1 matrices).

The relevant code is only 2 lines long, but it still bothers me to have several copies. What is the best way to achieve this?
[And how can I be sure that I have not forgotten another place where those special cases should be dealt with?]

Any function which is user accessible should certainly handle those inputs. Other fns should either handle those cases or give error or assert that they do not occur.

#4 Updated by John Abbott over 7 years ago

  • Status changed from Resolved to Closed
  • % Done changed from 80 to 100

#5 Updated by Anna Maria Bigatti almost 7 years ago

  • Estimated time set to 0.51 h

Also available in: Atom PDF