Is the derivation of REINFORCE wrong?












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In Reinforcement Learning (2nd edition) by Sutton and Barto, the REINFORCE update is derived as follows:



enter image description here



However, I am wondering why you can perform the transition from the second to third line, as both the first factor $G_t$ and the second factor are functions of the same random variables, $A_t$ and $S_t$ (sampled values), which are not necessarily independent. The expectation of two functions of random variables should only be reducible to the product of their expectations if the random variables are independent.










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    0












    $begingroup$


    In Reinforcement Learning (2nd edition) by Sutton and Barto, the REINFORCE update is derived as follows:



    enter image description here



    However, I am wondering why you can perform the transition from the second to third line, as both the first factor $G_t$ and the second factor are functions of the same random variables, $A_t$ and $S_t$ (sampled values), which are not necessarily independent. The expectation of two functions of random variables should only be reducible to the product of their expectations if the random variables are independent.










    share|improve this question







    New contributor




    minch is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.







    $endgroup$















      0












      0








      0





      $begingroup$


      In Reinforcement Learning (2nd edition) by Sutton and Barto, the REINFORCE update is derived as follows:



      enter image description here



      However, I am wondering why you can perform the transition from the second to third line, as both the first factor $G_t$ and the second factor are functions of the same random variables, $A_t$ and $S_t$ (sampled values), which are not necessarily independent. The expectation of two functions of random variables should only be reducible to the product of their expectations if the random variables are independent.










      share|improve this question







      New contributor




      minch is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.







      $endgroup$




      In Reinforcement Learning (2nd edition) by Sutton and Barto, the REINFORCE update is derived as follows:



      enter image description here



      However, I am wondering why you can perform the transition from the second to third line, as both the first factor $G_t$ and the second factor are functions of the same random variables, $A_t$ and $S_t$ (sampled values), which are not necessarily independent. The expectation of two functions of random variables should only be reducible to the product of their expectations if the random variables are independent.







      machine-learning reinforcement-learning policy-gradients






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      asked 11 mins ago









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