I would bet that you are doing something in C++ that shares some resource
between the workers and blocks all but one worker at a time.
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Sent from my phone. Please excuse my brevity.
sophie_brugie...@mpipsykl.mpg.de wrote:
>Dear all,
>
>I have an R script that uses Rcpp, and I have been trying to
>parallelize
>it using mclapply (I tried with the multicore and the parallel library)
>
>Sometimes (not always, interestingly), the CPU use for each core drops,
>usually so that the total over all cores reaches 100%, i.e., as fast as
>if
>using just one single core fully. I tried my code directly from within
>emacs, and also using a shell command - it happens either way.
>
>I suspect there might be some interaction between Rcpp and the
>multicore/parallel libraries. Did any R(cpp) user encounter such
>symptoms?
>
>Sophie
>
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>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.
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