Pipelined conjugate residual method. Pipelined Krylov Methods
This method has only a single non-blocking reduction per iteration, compared to 2 blocking for standard
non-blocking reduction is overlapped by the matrix-vector product, but not the preconditioner application.
KSPPIPECG, where the reduction is only overlapped with the matrix-vector product.
MPI configuration may be necessary for reductions to make asynchronous progress, which is important for performance of pipelined methods. See What steps are necessary to make the pipelined solvers execute efficiently?
Pieter Ghysels, Universiteit Antwerpen, Intel Exascience lab Flanders
P. Ghysels and W. Vanroose, “Hiding global synchronization latency in the preconditioned Conjugate Gradient algorithm”, Submitted to Parallel Computing, 2012.
KSP: Linear System Solvers, Pipelined Krylov Methods, What steps are necessary to make the pipelined solvers execute efficiently?,