Thanks Pallavi for reminding :) Yep it works when random probabilities are used.
-Prasen On Tue, Feb 10, 2009 at 2:20 PM, Pallavi Palleti < [email protected]> wrote: > Hi Prasen, > I faced the same issue and figured out that, when you use equal > probabilities for both P(s/z) and P(z/u), it will average out and finally > end up with the same probability that you have started with. In order to > make it work, one of it should be random either P(s/z) and P(z/u). Then it > will converge. > > Thanks > Pallavi > > prasenjit mukherjee wrote: > >> Hi, >> I have written a pig script which attempts to implement the EM algo for >> PLSI. For extremely simple case with the following data : >> transaction_log = (u1,s1), (u2,s2) >> z = 2 >> >> if I initialize the p(s|z) and p(z|u) with equal probabilities (all 0.5 >> ) >> I was expecting a convergence of results towards ==> p(z1|u1) ~ 1 and >> p(z2|u2) ~ 1. >> >> But it seems to get stuck with the same values after the first iteration. >> Is >> it because I am working with too less a data and getting stuck in a local >> minima or there is indeed a problem with my implementation which needs to >> be >> fixed. >> >> I also tried manually computing with those iterations and even then I am >> getting same values for p(s|z) and p(z|u) with which I had started. >> >> Any help is greatly appreciated. >> >> -Thanks, >> Prasen >> >> >> > >
