new function openmp_enabled() that informs the user if OpenMP is av…

…ailable or not.

NAMESPACE

@@ -11,6 +11,7 @@ S3method(tibble::as_tibble,fcwtr_scalogram)
 export(du)
 export(fcwt)
 export(fcwt_batch)
+export(openmp_enabled)
 export(u)
 importFrom(graphics,plot)
 importFrom(utils,setTxtProgressBar)

NEWS.md

@@ -18,6 +18,8 @@
 
 -   add more convenience S3 methods: `print()`, `[]`, `as.matrix()`, `rbind()`, `as_tibble()`.
 
+-   `openmp_enabled()`: new function to check for OpenMP support.
+
 -   add a [package logo](https://lschneiderbauer.github.io/fCWTr/logo.svg)
 
 # fcwtr 0.2.1

R/cpp11.R

@@ -1,5 +1,9 @@
 # Generated by cpp11: do not edit by hand
 
+has_openmp <- function() {
+  .Call(`_fCWTr_has_openmp`)
+}
+
 fcwt_raw <- function(signal, fs, f0, f1, fn, sigma, nthreads, scaletype, optplans, abs) {
   .Call(`_fCWTr_fcwt_raw`, signal, fs, f0, f1, fn, sigma, nthreads, scaletype, optplans, abs)
 }

R/fcwt.R

@@ -63,7 +63,9 @@
 #'
 #' @param n_threads
 #'  Number of threads used by the computation, if supported by your platform.
-#'  Defaults to 2 threads (to accomodate CRAN requirements).
+#'  Defaults to 2 threads (to accommodate CRAN requirements).
+#'  If [openmp_enabled()] returns `FALSE`, this argument is ignored, and
+#'  only a single thread is used.
 #'
 #' @return
 #'  The spectogram, a numeric real-valued matrix with dimensions

R/openmp.R

@@ -0,0 +1,28 @@
+
+#' Check for OpenMP support
+#'
+#' This function checks if OpenMP support is enabled. It is responsible for
+#' the multithreading capabilities of [fcwt()]. If OpenMP is not enabled
+#' the parameter `n_threads` of [fcwt()] is ignored.
+#'
+#' @details
+#' OpenMP can be used by the underlying fCWT library if
+#' * the fftw library on your platform was compiled with OpenMP support and
+#' * the fCWTr package itself was compiled with OpenMP support.
+#'
+#' When using pre-built package binaries (like it is typical when you are using
+#' R on Windows), whether or not these conditions are met, depend on the (CRAN)
+#' build server. They cannot be influenced by the package author.
+#'
+#' If the user is building the R package yourself, the user needs to make sure
+#' that the fftw library on her platform are built with OpenMP support.
+#' The fCWTr package is configured to use OpenMP if fftw-OpenMP support is
+#' available.
+#'
+#' @return ( `TRUE` | `FALSE` )
+#'  Returns `TRUE` if OpenMP support is enabled, `FALSE` otherwise.
+#'
+#' @export
+openmp_enabled <- function() {
+  has_openmp()
+}

_pkgdown.yml

@@ -21,6 +21,9 @@ reference:
   - print.fcwtr_scalogram
   - plot.fcwtr_scalogram
   - autoplot.fcwtr_scalogram
+- title: "Multithreading support"
+  contents:
+  - openmp_enabled
 - title: "Sample data"
   desc: >
     Sample signal data mainly used to generate examples. The signals consist

src/cpp11.cpp

@@ -5,6 +5,13 @@
 #include "cpp11/declarations.hpp"
 #include <R_ext/Visibility.h>
 
+// interface_fcwt.cpp
+cpp11::r_bool has_openmp();
+extern "C" SEXP _fCWTr_has_openmp() {
+  BEGIN_CPP11
+    return cpp11::as_sexp(has_openmp());
+  END_CPP11
+}
 // interface_fcwt.cpp
 std::vector<double> fcwt_raw(std::vector<double> signal, int fs, double f0, double f1, int fn, double sigma, int nthreads, bool scaletype, bool optplans, bool abs);
 extern "C" SEXP _fCWTr_fcwt_raw(SEXP signal, SEXP fs, SEXP f0, SEXP f1, SEXP fn, SEXP sigma, SEXP nthreads, SEXP scaletype, SEXP optplans, SEXP abs) {
@@ -15,7 +22,8 @@ extern "C" SEXP _fCWTr_fcwt_raw(SEXP signal, SEXP fs, SEXP f0, SEXP f1, SEXP fn,
 
 extern "C" {
 static const R_CallMethodDef CallEntries[] = {
-    {"_fCWTr_fcwt_raw", (DL_FUNC) &_fCWTr_fcwt_raw, 10},
+    {"_fCWTr_fcwt_raw",   (DL_FUNC) &_fCWTr_fcwt_raw,   10},
+    {"_fCWTr_has_openmp", (DL_FUNC) &_fCWTr_has_openmp,  0},
     {NULL, NULL, 0}
 };
 }

src/interface_fcwt.cpp

@@ -19,6 +19,15 @@ float dbl_to_float(const double &dbl) {
   return static_cast<float>(dbl);
 }
 
+[[cpp11::register]]
+cpp11::r_bool has_openmp() {
+  #ifdef SINGLE_THREAD
+    return(false);
+  #else
+    return(true);
+  #endif
+}
+
 [[cpp11::register]]
 std::vector<double> fcwt_raw(
     std::vector<double> signal,

tests/testthat/test-openmp.R

@@ -0,0 +1,5 @@
+test_that("openmp() works", {
+  expect_true(
+    openmp_enabled() == TRUE |  openmp_enabled() == FALSE
+  )
+})