Implemented A2C on Pendulum Problem

[raghav9-97]

Used Tejank's a2c.jl model on Cartpole problem.

[sidhantnagpal]

I think you should retain the authorship of the code. Are there any new changes in this?

[raghav9-97]

Yup, I myself wrote the loop implementation and used helper functions and hyperparams from earlier code.

[DhairyaLGandhi]

Maybe it would be worth looking at convergence further. There are a couple of comments (plotting) still in the script also.

[raghav9-97]

I have deliberately commented them out as a user needs to explicitly import Plots in order to render Pendulum environment. I will look out for convergence of the model.