Riga finished hw4! #32
                
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尽力优化了hw4!
优化前:
Initial energy: -13.414000
Final energy: -13.356842
Time elapsed : 2261 ms
优化后:
Initial energy: -13.414016
Final energy: -13.356915
Time elapsed : 263 ms
主要优化点(主要针对step函数):