Problems calculating determinant of larger (>= 4x4) matrices (Bug #2715)

Added by Jukka Holappa about 12 years ago. Updated about 12 years ago.

Status:Cancelled Start date:2013-01-18
Priority:Normal Due date:
Assignee:Vadim Pisarevsky % Done:

0%
Category:core
Target version:-
Affected version: Operating System:
Difficulty: HW Platform:
Pull request:

Description

cv::determinant() has hardcoded solutions for 2x2 and 3x3 matrices and uses LU for larger ones.

For some reason trying to calculate determinant of 4x4 CV_64FC1 matrices fail and always return 0.

For example I created a random 4x4 matrix M:
0.8147 0.6324 0.9575 0.9572
0.9058 0.0975 0.9649 0.4854
0.1270 0.2785 0.1576 0.8003
0.9134 0.5469 0.9706 0.1419

When using MATLAB to calculate M's determinant I get -0.0262. OpenCV with CV_64FC1 matrices returns 0. If I use CV_32FC1 matrix type, I get 0.00119369 which is still not correct.

Much simpler cases fail as well:
det(I) where I is an identity matrix of any NxN dimensions should be 1.

When calculating using OpenCV:
Det 3x3 identity with doubles: 1
Det 3x3 identity with floats: 1
Det 4x4 identity with doubles: 0
Det 4x4 identity with floats: 0

Something with generic solution is seriously broken at the moment. This was tested with latest Git version from yesterday.

Associated revisions

Revision 7ac5c367
Added by Alexander Alekhin almost 11 years ago

Merge pull request #2715 from akarsakov:fix_corner_min_eigen

History

#1
Updated by Vadim Pisarevsky about 12 years ago

looks like the bug is in your code, or your compiler is buggy.
Here is what I get on Mac with Xcode 4.5.2 (clang 4.1 compiler) and the following code:

double a[] = {
    0.8147, 0.6324, 0.9575, 0.9572,
    0.9058, 0.0975, 0.9649, 0.4854,
    0.1270, 0.2785, 0.1576, 0.8003,
    0.9134, 0.5469, 0.9706, 0.1419
};
Mat A(4, 4, CV_64F, a);
printf("det(64f)=%g, det(32f)=%g\n",
           determinant(A), determinant(Mat_<float>(A)));

output:

det(64f)=-0.0261654, det(32f)=-0.0261654

  • Status changed from Open to Cancelled

#2
Updated by Jukka Holappa about 12 years ago

Thanks for quick feedback.

I'm currently suspecting my compiler as I needed to upgrade it very recently.

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