[Bug 1214482] Re: Not-grouping dependent packages in Phased Updates changes propability distribution for entire group of dependent packages.

[Michael Vogt]

Thanks for your bugreport and sorry for the late reply.

Your analysis is correct, the probability changed for dependent
packages.

However because of the way we seed the random number generator its less
of a issue in a lot of the practical cases. We use the (source package
name, update version, client-machine-id) as the input for the RNG. This
means that in the linux example all packages have the same probability
because they come from the same source package.

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https://bugs.launchpad.net/bugs/1214482

Title:
  Not-grouping dependent packages in Phased Updates changes propability
  distribution for entire group of dependent packages.

Status in “update-manager” package in Ubuntu:
  New

Bug description:
  I assume that you decided for uniform distribution in the random
  number generator. If group of dependent packages is installed only
  when all phased-update-percentage values (for each package) are
  smaller than the present percentage on server - it will change
  probability distribution for the whole group of packages.

  Just run this:

  figure(1)
  hist(rand(1,100000))
  for i = 2:10
  	figure(i)
  	hist(max(rand(i,100000)))
  endfor

  in octave and look at histograms for i>1 (i is the number of dependent
  packages).

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