  In this paper, we propose two mixed precision algorithms for Block-Jacobi
preconditioner(BJAC): a fixed low precision strategy and an adaptive precision
strategy. We evaluate the performance improvement of the proposed mixed
precision BJAC preconditioners combined with the preconditioned conjugate
gradient algorithm using problems including diffusion equations and radiation
hydrodynamics equations. Numerical results show that, compared to the uniform
high precision PCG algorithm, the mixed precision preconditioners can achieve
speedups from 1.3 to 1.8 without sacrificing accuracy. Furthermore, we observe
the phenomenon of convergence delay in some test cases for the mixed precision
preconditioners, and further analyse the matrix features associate with the
convergence delay behavior.
