Modified Block BiCGSTAB for Lattice QCD

Understand

We present results for application of block BiCGSTAB algorithm modified by the QR decomposition and the SAP preconditioner to the Wilson-Dirac equation with multiple right-hand sides in lattice QCD on a $32^3 \times 64$ lattice at almost physical quark masses.

• The QR decomposition improves convergence behaviors in the block BiCGSTAB algorithm suppressing deviation between true residual and recursive one.
• The SAP preconditioner applied to the domain-decomposed lattice helps us minimize communication overhead.
• We find remarkable cost reduction thanks to cache tuning and reduction of number of iterations.