Every invocation of R is creating 63 sub processes
Rscript --vanilla -e 'Sys.sleep(5)' & pstree -p $! | grep -c '{R}'
# 63
where pstree looks something like this
R(2562809)─┬─{R}(2562818)
├─{R}(2562819)
...
├─{R}(2562878)
├─{R}(2562879)
└─{R}(2562880)
is this expected behavior?
This is a 72 core machine with debian 9.3, R==3.4.3, blas==3.7.0, and openmp==2.0.2
dpkg-query -l '*blas*' 'r-base' '*lapack*' '*openmp*'|grep ^ii
ii libblas-common 3.7.0-2 amd64 Dependency package for all BLAS implementations
ii libblas-dev 3.7.0-2 amd64 Basic Linear Algebra Subroutines 3, static library
ii libblas3 3.7.0-2 amd64 Basic Linear Algebra Reference implementations, shared library
ii liblapack-dev 3.7.0-2 amd64 Library of linear algebra routines 3 - static version
ii liblapack3 3.7.0-2 amd64 Library of linear algebra routines 3 - shared version
ii libopenblas-base 0.2.19-3 amd64 Optimized BLAS (linear algebra) library (shared library)
ii libopenmpi-dev 2.0.2-2 amd64 high performance message passing library -- header files
ii libopenmpi2:amd64 2.0.2-2 amd64 high performance message passing library -- shared library
ii libopenmpt0:amd64 0.2.7386~beta20.3-3+deb9u2 amd64 module music library based on OpenMPT -- shared library
ii openmpi-bin 2.0.2-2 amd64 high performance message passing library -- binaries
ii openmpi-common 2.0.2-2 all high performance message passing library -- common files
ii r-base 3.4.3-1~stretchcran.0 all GNU R statistical computation and graphics system
R is using openblas and openmp libraries
Rscript --vanilla -e 'Sys.sleep(1)' & lsof -p $! | grep -E -i 'blas|lapack|parallel|omp'
[1] 2574896
lsof: WARNING: can't stat() tracefs file system /sys/kernel/debug/tracing
Output information may be incomplete.
R 2574896 foranw mem REG 0,20 13931603 /usr/lib/libopenblasp-r0.2.19.so (path dev=0,21)
R 2574896 foranw mem REG 0,20 13931604 /usr/lib/openblas-base/libblas.so.3 (path dev=0,21)
R 2574896 foranw mem REG 0,20 13840156 /usr/lib/x86_64-linux-gnu/libgomp.so.1.0.0 (path dev=0,21)
R is (famously) single-core.
I suspects this comes from libopenblas-base which is (also known to be) multi-core.
Contrast this with our rocker container which uses libblas3 -- single-threaded, not optmized:
> system("pstree")
bash───R───sh───pstree
> system("ps -ax")
PID TTY STAT TIME COMMAND
1 pts/0 Ss 0:00 /bin/bash
579 pts/0 S+ 0:00 /usr/lib/R/bin/exec/R
583 pts/0 S+ 0:00 sh -c ps -ax
584 pts/0 R+ 0:00 ps -ax
>
As Debian maintainer for R, I take advantage of the fact that we have several BLAS / LAPACK builds. Base can be ok, OpenBLAS often is faster (but be careful when you then launch multiple cores from R via the different mechanisms) and there is also Atlas. What is "best" will always get a fimr "it depends".