F = 
   ((1. - Subscript[p, 4])^(-Subscript[p, 3]) - (1. - Subscript[p, 4]*
     Exp[-Subscript[p, 1]*Subscript[x, i]^Subscript[p,2]])^(-Subscript[p,3]))/
     ((1. - Subscript[p, 4])^(-Subscript[p, 3]) - 1.)

 f = FullSimplify[D[F, Subscript[x, i]]]

 L := Product[f, {i, 1, n}]  // AbsoluteTiming      

In Mathematica 7.0, how can I get the Product expression shown above to evaluate in a reasonable time without specifying n?.

  • $\begingroup$ Welcome to Mathematica.SE! 1) As you receive help, try to give it too, by answering questions in your area of expertise. 2) Take the tour and check the faqs! 3) When you see good questions and answers, vote them up by clicking the gray triangles, because the credibility of the system is based on the reputation gained by users sharing their knowledge. Also, please remember to accept the answer, if any, that solves your problem, by clicking the checkmark sign! $\endgroup$ – user9660 Oct 28 '15 at 7:43
  • 3
    $\begingroup$ Do you expect it to have a nice form? It shouldn't, that I can see. $\endgroup$ – Patrick Stevens Oct 28 '15 at 7:45
  • $\begingroup$ Notice that if I remove p1*p2*p3*p4 from density function f then Product[] works fine even though it takes long time. The question is why product[] does not work in the previous density function f ? $\endgroup$ – aaa Oct 28 '15 at 9:23

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