Tolerance in LUQ decomposition

Hello,

I found the code for the LUQ decomposition here http://www.mathworks.com/matlabcentral/fileexchange/11120-null-space-of-a-sparse-matrix/content/sparse%20null/luq.m

In order to perform the decomposition, a tolerance value uses in separating zero and nonzero values is required.

I was wondering which tolerance value would be suitable for that problem. In particular, I will use LUQ decomposition in order to determine the rank of a matrix A, and for that I would look the size of the matrix U that comes out from the LUQ routine.

Any suggestions?

Thank you in advance