Comparison of Multi-quark Matrix Inversion Algorithms
  We test iterative algorithms, MR, QMR$\gamma_5$ and BiCG$\gamma_5$, to compare their efficiency in matrix inversion with multi-quarks (shifted matrices) within one iteration process. Our results on the 8^3 x 12 and 16^3 x 24 show that MR admits multi-quark calculation with less memory requirement, whereas QMR is faster for the single quark calculation. 
He-Ping Ying, Shao-Jing Dong, and Keh-Fei Liu