# Test matrices for large sparse overdetermined system of linear equations

I'm working on some c++ code to solve (conjugate gradient, least squares conjugate gradient, LSQR,..) large sparse overdetermined systems of linear equations. There is a twist to my matrices and the system they're running on, that's why I code the solver myself.

For testing, debugging and benchmarking purposes I'm looking for some test matrix-vector-problems with well known solutions. I would like to be able to generate such systems for varying matrix size N x M. (Typically I deal with matrices of the size 10^7 x 10^5 with 10^9 non-zero elements.)

Do you know any such matrix-vector-systems what can easily be generated?