[Rcpp-devel] RcppArmadillo BLAS/LAPACK force number of threads to 1

[Scott Ritchie]

Well that's frustrating.

I've tried the OpenMPController package without success, and tried to
explicitly disable BLAS in the Armadillo headers and removing the linking
code in the Makevars files.

If my reading of this thread:
http://lists.r-forge.r-project.org/pipermail/rcpp-devel/2012-June/003888.html
is correct, I should be able to switch to RcppEigen since it uses its own
routines.


On 12 August 2014 14:07, Dirk Eddelbuettel <edd at debian.org> wrote:

>
> On 11 August 2014 at 19:23, Yixuan Qiu wrote:
> | Good point by Dirk.
> |
> | And why not just adding a line "export OPENBLAS_NUM_THREADS=1" to your
> .bashrc
> | file, or compiling OpenBlas again by setting NUM_THREADS = 1 in the
> | Makefile.rule?
>
> Unless you insist on it you should not need to recompile OpenBLAS.
>
> You should have a choice of distributions or system which does this right.
>
> Dirk
>
> |
> | Best,
> | Yixuan
> |
> |
> | 2014-08-11 18:55 GMT-04:00 Dirk Eddelbuettel <edd at debian.org>:
> |
> |
> |     Hi Scott,
> |
> |
> |     On 12 August 2014 at 08:43, Scott Ritchie wrote:
> |     | Hi Everyone,
> |     |
> |     | I'm having trouble with restricting the Armadillo function
> "svd_econ" to
> |     run on
> |     | a single thread.
> |     |
> |     | I am able to restrict it if I `export OPENBLAS_NUM_THREADS=1`
> before
> |     opening an
> |     | R session, but not from within R
> (`Sys.setenv(OPENBLAS_NUM_THREADS=1)`
> |     has no
> |     | effect).
> |     |
> |     | I'm wondering if theirs an option native to
> armadillo/RcppArmadillo that
> |     I'm
> |     | missing to enable me to:
> |     |
> |     |   • Restrict the number of threads used to 1
> |     |   • In a library agnostic manner (i.e. if the user has a different
> LAPACK
> |     or
> |     |     BLAS library installed).
> |     |
> |     | or if I can "trick" Rcpp into thinking the machine only has 1 core?
> |
> |     I fear you may be misstating / misdiagnosing the problem.
> |
> |     I am fairly certain that there is not a single line in Rcpp or
> |     (Rcpp)Armadillo which sets thread counts for your LAPACK / BLAS.
> |
> |     Rather, and this is a point that I tried to make in the
> 'Benchmarking GPUs
> |     and CPUs on Debian-based systems' package (gcbd on CRAN etc) and its
> |     vignette
> |     is that __BLAS and LAPACK sit behind a standardized interface__ and
> can be
> |     installed / swapped via plug and play. (Which in turn enables the
> |     benchmarking ...)
> |
> |     If you're on a Debian-based system, just remove openblas and use
> atlas.
> |     Case
> |     closed.  Atlas will not multithread (unless something changed
> recently).
> |
> |     There is also a helper function or package somewhere, and a post by
> Claudia
> |     Beleites on StackOverflow, which show the explicit function call to
> reset
> |     OpenBLAS in its count.  But if everything else fails -- just use a
> |     different
> |     BLAS.  I sometimes do that too when I use multicore / parallel to
> launch
> |     multiple R jobs and each one of those should not spawn additional
> linear
> |     algebra threads.
> |
> |     Hope this helps,  Dirk
> |
> |
> |
> |     | Regards,
> |     |
> |     | Scott Ritchie
> |     | _______________________________________________
> |     | Rcpp-devel mailing list
> |     | Rcpp-devel at lists.r-forge.r-project.org
> |     |
> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
> |
> |     --
> |     http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org
> |     _______________________________________________
> |     Rcpp-devel mailing list
> |     Rcpp-devel at lists.r-forge.r-project.org
> |
> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
> |
> |
> |
> |
> | --
> | Yixuan Qiu <yixuan.qiu at cos.name>
> | Department of Statistics,
> | Purdue University
>
> --
> http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org
>
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