# Singularity of Positive Semi Definite Matrices

#### fawaz

##### New member
Hello,I'm given a sparse symmetric positive semi definite matrix and I want to check whether it is singular or not.What's a quick way to do that? (I can't do any kind of factorization because the matrix can be huge)I know the following:- if any of the diagonal entries is zero, then the matrix is singular (because then I have a row and a column of zeros)- If I multiply the matrix by a vector of ones and I get zeros everywhere, then the matrix is singular.What other cases am I missing?Thank youMohammad