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OpenMP startup and CI refinements (#500)
* On macOS also install and show cores * Trying alternate macOS config for openmp * Shorten and reduce to two * Refine openmp thread count setting at startup * Agree on name for thread count environment-stored variable * And a #nocov end tag cleanup
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‎.github/workflows/ci.yaml‎

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Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@ jobs:
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include:
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- { name: container, os: ubuntu-latest, container: rocker/r2u4ci }
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- { name: macos, os: macos-latest, openmp: yes }
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- { name: macos, os: macos-latest, openmp: no }
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#- { name: macos, os: macos-latest, openmp: no }
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#- { name: ubuntu, os: ubuntu-latest }
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@@ -30,25 +30,32 @@ jobs:
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- name: Setup
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uses: eddelbuettel/github-actions/r-ci@master
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- name: OpenMP for macOS
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if: ${{ matrix.os == 'macos-latest' && matrix.openmp == 'yes' }}
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run: |
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curl -fsSL https://raw.githubusercontent.com/coatless-shell/openmp/main/install-openmp.sh | bash -s -- --yes
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mkdir -p ~/.R
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cat <<EOF > ~/.R/Makevars
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CPPFLAGS += -Xclang -fopenmp
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LDFLAGS += -lomp
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EOF
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# - name: OpenMP for macOS
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# if: ${{ matrix.os == 'macos-latest' && matrix.openmp == 'yes' }}
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# run: |
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# curl -fsSL https://raw.githubusercontent.com/coatless-shell/openmp/main/install-openmp.sh | bash -s -- --yes
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# mkdir -p ~/.R
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# cat <<EOF > ~/.R/Makevars
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# CPPFLAGS += -Xclang -fopenmp
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# LDFLAGS += -lomp
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# EOF
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# cat ~/.R/Makevars
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# echo -n "R CMD config CXX: "; R CMD config CXX
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# echo -n "R CMD config CPPFLAGS: "; R CMD config CPPFLAGS
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# echo -n "R CMD config LDFLAGS: "; R CMD config LDFLAGS
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# echo -n "R CMD config SHLIB_CXXLD: "; R CMD config SHLIB_CXXLD
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# echo -n "R CMD config SHLIB_CXXLDFLAGS: "; R CMD config SHLIB_CXXLDFLAGS
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- name: Show config on macOS
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- name: OpenMP for macOS
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if: ${{ matrix.os == 'macos-latest' && matrix.openmp == 'yes' }}
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run: |
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cat ~/.R/Makevars
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echo -n "R CMD config CXX: "; R CMD config CXX
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echo -n "R CMD config CPPFLAGS: "; R CMD config CPPFLAGS
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echo -n "R CMD config LDFLAGS: "; R CMD config LDFLAGS
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echo -n "R CMD config SHLIB_CXXLD: "; R CMD config SHLIB_CXXLD
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echo -n "R CMD config SHLIB_CXXLDFLAGS: "; R CMD config SHLIB_CXXLDFLAGS
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curl -O https://mac.r-project.org/openmp/openmp-17.0.6-darwin20-Release.tar.gz
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sudo tar fvxz openmp-17.0.6-darwin20-Release.tar.gz -C /
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rm openmp-17.0.6-darwin20-Release.tar.gz
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sudo xcode-select -s /Applications/Xcode_16.2.app
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echo "MACOSX_DEPLOYMENT_TARGET=11.0" >> $GITHUB_ENV
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echo "xcode is set: $(xcode-select --print-path)"
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echo "using SDK: $(xcrun --show-sdk-version)"
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- name: Configure
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run: ./configure; cat src/Makevars
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- name: Test
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run: ./run.sh run_tests
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- name: Install and Verify on macOS
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if: ${{ matrix.os == 'macos-latest' }}
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run: |
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R CMD INSTALL .
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Rscript -e 'RcppArmadillo::armadillo_get_number_of_omp_threads()'
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- name: Coverage
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if: ${{ matrix.os == 'ubuntu-latest' }}
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env:

‎ChangeLog‎

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Original file line numberDiff line numberDiff line change
@@ -1,3 +1,9 @@
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2026-01-03 Dirk Eddelbuettel <edd@debian.org>
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* R/init.R: Expand openmp core count logic respecting Ncpus and
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OMP_THREAD_LIMIT else setting all cores; add startup message
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* man/RcppArmadillo-package.Rd: Document thread count setting options
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2025-12-16 Dirk Eddelbuettel <edd@debian.org>
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* DESCRIPTION (Version, Date): RcppArmadillo 15.2.3-1

‎R/init.R‎

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## init.R: Startup
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##
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## Copyright (C) 2023 Dirk Eddelbuettel
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## Copyright (C) 2023-2026 Dirk Eddelbuettel
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##
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## This file is part of RcppArmadillo.
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##
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.pkgenv <- new.env(parent=emptyenv())
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.onLoad <- function(libname, pkgname) {
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.pkgenv[["omp_threads"]] <- armadillo_get_number_of_omp_threads() # #nocov
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.onLoad <- function(libname, pkgname) { # nocov start
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## simple fallback: 'Ncpus' (if set) or else all cpus seen by OpenMP
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ncores <- getOption("Ncpus", armadillo_get_number_of_omp_threads())
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## consider OMP_THREAD_LIMIT (cf Writing R Extensions), gets NA if envvar unset
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ompcores <- as.integer(Sys.getenv("OMP_THREAD_LIMIT"))
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## keep the smaller value, omitting NA
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ncores <- min(na.omit(c(ncores, ompcores)))
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.pkgenv[["omp_threads"]] <- ncores
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armadillo_throttle_cores(ncores)
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}
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.onAttach <- function(libname, pkgname) {
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if (interactive()) {
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packageStartupMessage("RcppArmadillo ", packageVersion("RcppArmadillo"),
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" using ", .pkgenv[["omp_threads"]], " cores. See ",
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"'help(\"RcppArmadillo-package\")' for details.")
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}
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}
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##' Throttle (or Reset) (Rcpp)Armadillo to Two Cores
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armadillo_reset_cores <- function() {
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n <- .pkgenv[["omp_threads"]]
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armadillo_set_number_of_omp_threads(n)
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}
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} # nocov end

‎man/RcppArmadillo-package.Rd‎

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\alias{RcppArmadillo}
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\alias{RcppArmadilloExample}
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\docType{package}
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\title{
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R and Armadillo Integration
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}
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\description{
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The package brings the power of Armadillo to R.
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}
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\title{R and Armadillo Integration}
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\description{The package brings the power of Armadillo to R.}
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\section{Armadillo}{
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\code{Armadillo} is a C++ linear algebra library, aiming towards a good
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balance between speed and ease of use.
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Armadillo has been primarily developed at NICTA (Australia) by Conrad
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Sanderson, with contributions from around the world.
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}
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\section{RcppArmadillo}{
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\code{RcppArmadillo} acts as a bridge between \code{Rcpp} and \code{Armadillo},
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allowing the programmer to write code using Armadillo classes that integrate
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seemlessly with \code{R} via \code{Rcpp}.
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}
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\section{Using RcppArmadillo}{
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The simplest way to get started is to create a skeleton of a package
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using \code{RcppArmadillo}. This can be done conveniently by the
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\code{\link{RcppArmadillo.package.skeleton}}
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function.
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The important steps are
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\itemize{
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\item Include the \code{RcppArmadillo.h} header file, which also includes
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\code{armadillo.h}.
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\item Import Rcpp, and LinkingTo Rcpp and RcppArmadillo by adding these lines to
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the DESCRIPTION file:
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\preformatted{
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Imports: Rcpp (>= 0.11.0)
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LinkingTo: Rcpp, RcppArmadillo
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}
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\item Link against the BLAS and LAPACK libraries, by adding this line
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in the \code{Makevars} and \code{Makevars.win} files:
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\preformatted{PKG_LIBS = $(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS) }
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}
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}
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\section{Support}{
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Please use the Rcpp-devel mailing list on r-forge
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for questions about RcppArmadillo (subscribe first).
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\url{https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel}
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\section{Threading}{
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The Armadillo library can take advantage of OpenMP to execute computations in
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parallel via multi-threaded code. The number of cores uses can be set (or
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retrieved) explicitly via helper functions \code{armadillo_get_number_of_omp+threads()} and
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\code{armadillo_set_number_of_omp_threads()}. A default value is stored at package startup; it
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recognises R option value \code{Ncpus} and environment variable
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\code{OMP_THREAD_LIMIT}. Additional helper functions
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\code{armadillo_throttle_cores()} and \code{armadillo_reset_cores()} are
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available to (temporarily) lower the number of cores uses and to reset to
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the package default value set at startup.
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}
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\author{
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For RcppArmadillo: Dirk Eddelbuettel, Romain Francois, Doug Bates and
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Binxiang Ni
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"RcppArmadillo: Accelerating R with high-performance C++ linear algebra",
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Computational Statistics and Data Analysis, 2014, 71, March, pages
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1054-1063, \doi{10.1016/j.csda.2013.02.005}.
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)
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}
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\keyword{ package }
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\keyword{ programming }
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\keyword{ interface }
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\keyword{package}
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\keyword{programming}
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\keyword{interface}

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