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当发送一个结构数组时，确定对于每一结构的大小MPI和C编译器有同样的值是很重要的。最可移植的方法是将MPI-UB添加到结构的结尾的定义中。 

/* initialize types and displs with addresses of items */ 
MPI_Address( &cmdline.display, &displs[0] ); 
MPI_Address( &cmdline.maxiter, &displs[1] ); 
MPI_Address( &cmdline.xmin,    &displs[2] ); 
MPI_Address( &cmdline.width,   &displs[3] ); 
MPI_Address( &cmdline+1,       &displs[4] ); 
types[0] = MPI_CHAR; 
types[1] = MPI_INT; 
types[2] = MPI_DOUBLE; 
types[3] = MPI_INT; 
types[4] = MPI_UB; 
for (i = 4; i >= 0; i--) 
    displs[i] -= displs[0]; 
MPI_Type_struct( 5, blockcounts, displs, types, &cmdtype ); 
MPI_Type_commit( &cmdtype );

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