[Bioc-devel] bplapply Processes Sometimes Stall

Morgan, Martin Martin.Morgan at roswellpark.org
Mon Dec 28 18:08:41 CET 2015

Hi Dario -- This didn't cause problems for me. One thing you might do is to re-use the MulticoreParam() like this

    param = bpstart(MulticoreParam(25))
    lapply(1:20, function(variety) bplapply(1:100, function() {}, BPPARAM = param))

Also there have been a number of changes in devel and if possible it would be good to know whether the problem still appears there.

It might be interesting to see the number of connections open when the process hangs, from the command line while R is still running

   ~$ lsof -i |grep -c R

From: Bioc-devel [bioc-devel-bounces at r-project.org] on behalf of Dario Strbenac [dstr7320 at uni.sydney.edu.au]
Sent: Sunday, December 27, 2015 8:00 PM
To: bioc-devel at r-project.org
Subject: [Bioc-devel] bplapply Processes Sometimes Stall

Good day,

I have a minimal example of bplapply stalling.

results <- lapply(1:20, function(variety)
  message("Variety", variety)
  bplapply(1:100, function(index) {res <- list(sample(20000), sample(c("Healthy", "Disease"), 20000, replace = TRUE)); res}, BPPARAM = MulticoreParam(workers = 25))

It sometimes stalls on no particular iteration, but other times it runs all 20 iterations and returns to the R command prompt. It's not reproducible when the stall happens. I am trying to find the cause of a cross-validation loop that progresses for a few hours, then stalls. When the stall happens, two or three of the R processes appear to be using 100% CPU whereas the others are finished, according to the output of top. The server was previously running R 3.1.2 and Debian 7 and this didn't ever happen. The server has 48 processors.

If I set workers to 5, it always completes the loop and returns to the prompt. Using mclapply with mc.cores set to 25 also always works, so the problem is with bplapply.

R version 3.2.3 (2015-12-10)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Debian GNU/Linux 8 (jessie)

 [1] LC_CTYPE=C.UTF-8       LC_NUMERIC=C           LC_TIME=C.UTF-8        LC_COLLATE=C.UTF-8

attached base packages:
[1] parallel  stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] BiocParallel_1.4.3

loaded via a namespace (and not attached):
[1] futile.logger_1.4.1  lambda.r_1.1.7       futile.options_1.0.0

Dario Strbenac
PhD Student
University of Sydney
Camperdown NSW 2050
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