Files:
    cg.c : main functions, the implementaion of conjugate gradient method.
    globals.h : some data defination.
    common : functions for verification and time caculation.
    bin : excutable output directory.
    Makefile, make.common : make systems.

Build up:
    make DATASIZE=[LARGE|MEDIUMN|SMALL]
    (If not assign DATASIZE, default will be mediumn)
    Please do make clean if you want to change datasize.

Check correctness:
    Main function contains verification information, it will show VERIFICATION SUCCESSFUL/FAILED to indicate the correctness of the program.