From paciorek at stat.berkeley.edu  Sat Dec  6 02:36:00 2014
From: paciorek at stat.berkeley.edu (Chris Paciorek)
Date: Fri, 5 Dec 2014 17:36:00 -0800
Subject: [Rd] does parLapplyLB do load-balancing?
Message-ID: <CAG=M9LrfOFMp0wT1rR3n7sumsNrscGBDS-8bkdzOXS=45jV9KQ@mail.gmail.com>

Looking at parLapplyLB, one sees that it takes in X and then passes
splitList(X, length(cl)) to clusterApplyLB, which then calls
dynamicClusterApply.  Thus while dynamicClusterApply does handle tasks
in a load-balancing fashion, sending out individual tasks as previous
tasks complete, parLapplyLB preempts that by splitting up the tasks in
advance into as many groups of tasks as there are cluster processes.
This seems to defeat the purpose of load-balancing and of the manner
in which dynamicClusterApply is coded.

This question basically repeats a question posed in 2013 -- see
http://r.789695.n4.nabble.com/parLapplyLB-Load-balancing-tt4671848.html

I'm reposting because there doesn't seem to have been any response to
the previous posting, and it looks like the issue is still present in
R 3.1 so it seems asking again if this is the intended behavior of
parLapplyLB.

I'm using R 3.1.1 and the 3.1.1 version of the parallel package under
Ubuntu 14.04, but the code appears to be the same in R-devel.


Chris


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[Rd] does parLapplyLB do load-balancing?
Chris Paciorek