  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.
