[R] snow and Rmpi, delayed starting-times at nodes

Markus Schmidberger schmidb at ibe.med.uni-muenchen.de
Fri Nov 2 16:37:27 CET 2007


we use R version 2.6.0, Rmpi_0.5-5 and snow_0.2-9 and have a parallel 
call like this:

clusterApply(cluster, input.list, function(input, data1, type) {  ....   
}, data1, type )

We now have the problem, that the processes at the nodes start delayed. 
This means for example, node 4 starts its calculation when node 1 is 
finished.(see the attached figure)
Therefore we have a lot of loss in our computation time.

Our messages are not very big:
input.list = list of vectors. Each vector has 10 strings
data1 = one integer
type = one string

What can we do to improve the speed?


Dipl.-Tech. Math. Markus Schmidberger

Ludwig-Maximilians-Universität München
IBE - Institut für medizinische Informationsverarbeitung,
Biometrie und Epidemiologie
Marchioninistr. 15, D-81377 Muenchen
URL: http://ibe.web.med.uni-muenchen.de 
Mail: Markus.Schmidberger [at] ibe.med.uni-muenchen.de

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