Merge pull request #112 from cindytsai/Refactor #18

Job	Run time
parallel (-DUSE_PYBIND11=ON, pybind11)	8m 18s
serial (-DUSE_PYBIND11=ON, pybind11)	1m 1s
parallel (-DUSE_PYBIND11=OFF, pure_python)	5m 52s
serial (-DUSE_PYBIND11=OFF, pure_python)	42s
	15m 53s

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