使用MPI计算Jacobi迭代，文件夹里有两个CPP文件，jacobi_std.cpp是标准的Jacobi程序（串行程序），mpi.cpp是MPI版本-Jacobi iterative calculation using MPI, folders, there are two CPP file, jacobi_std.cpp is the standard Jacobi procedure (serial program), mpi.cpp is the MPI version