Block variants of the COCG and COCR methods for solving complex   symmetric linear systems with multiple right-hand sides
  In the present study, we establish two new block variants of the Conjugate Orthogonal Conjugate Gradient (COCG) and the Conjugate A-Orthogonal Conjugate Residual (COCR) Krylov subspace methods for solving complex symmetric linear systems with multiple right hand sides. The proposed Block iterative solvers can fully exploit the complex symmetry property of coefficient matrix of the linear system. We report on extensive numerical experiments to show the favourable convergence properties of our newly developed Block algorithms for solving realistic electromagnetic simulations. 
Xian-Ming Gu, Bruno Carpentieri, Ting-Zhu Huang, Jing Meng
math.NA