[Rcpp-devel] R limiting the number of child threads

Dirk Eddelbuettel edd at debian.org
Mon Feb 4 19:37:23 CET 2013

On 4 February 2013 at 17:47, Yan Zhou wrote:
| I have a C++ library for parallel implementation of Sequential Monte Carlo
| algorithms. It can use some different programming models, OpenMP, Intel TBB,
| Intel Cilk, C++11 <thread>, and others. Everything worked fine so far.

Wow. You're way ahead of me. With OpenMP, and noticed that it uses the same
environment variable that Intel MKL uses. I suspect you may find it (and the
related ones) useful for Cilk and TBB too. Copied straight from the
libgomp-4.7 docs (in package gcc-4.7-doc on my Ubuntu box):

  3.4 `OMP_NUM_THREADS' - Specifies the number of threads to use
       Specifies the default number of threads to use in parallel
       regions. The value of this variable shall be a comma-separated
       list of positive integers; the value specified the number of
       threads to use for the corresponding nested level. If undefined
       one thread per CPU is used.
  _See also_:
       *note omp_set_num_threads::
       OpenMP specifications v3.1 (http://www.openmp.org/), section 4.2
I seem to recall that the R package parallel uses the same variables, so if
you behaviour that differs between standalone C++ code and code called from
R, check there too.

Hope this helps, Dirk

Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com  

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