Do we need -ltbb -ltbbmalloc on Linux and macOS?

[krlmlr]

Without these, compilation fails in a package that uses parallelReduce() with a Worker . (Compilation works on Windows with the same package.) I haven't checked if work happens in parallel when I add these flags.

RcppParallel::RcppParallelLibs()
RcppParallel:::tbbLdFlags()
#> [1] ""

^{Created on 2020-08-30 by the reprex package (v0.3.0)}

Example package

• Baseline: https://github.com/krlmlr/RcppParallelReprex
• Manually link TBB: Branch fix1
• Don't use TBB: Branch fix2

I was unable to whip up a reprex using Rcpp::compileFunction() .

Error message

undefined symbol: _ZN3tbb4task13note_affinityEt

[kevinushey]

Can you share the compilation output you're seeing as well?

I think the problem here is that RcppParallel loads the requisite TBB libraries in its own .onLoad() handler here:

RcppParallel/R/hooks.R

Lines 5 to 28 in 394a729

	.onLoad <- function(libname, pkgname) {
	# load tbb and tbbmalloc on supported platforms
	tbb <- tbbLibPath()
	if (!is.null(tbb)) {
	if (!file.exists(tbb)) {
	warning(paste("TBB library", tbb, "not found."))
	} else {
	dllInfo <<- dyn.load(tbb, local = FALSE, now = TRUE)
	}
	}
	tbbMalloc <- tbbLibPath("malloc")
	if (!is.null(tbbMalloc)) {
	if (!file.exists(tbbMalloc)) {
	warning(paste("TBB malloc library", tbbMalloc, "not found."))
	} else {
	mallocDllInfo <<- dyn.load(tbbMalloc, local = FALSE, now = TRUE)
	}
	}
	# load the package library
	library.dynam("RcppParallel", pkgname, libname)
	}

But because the package only links to RcppParallel, and doesn't import it (ie: it doesn't require RcppParallel to be loaded beforehand) then the TBB libraries don't get loaded and compilation fails.

The fix here would be to explicitly force the RcppParallel namespace to be loaded before loading the package.

[kevinushey]

A hacky way of doing this is to add:

Imports: RcppParallel

to the package DESCRIPTION, and

importFrom(RcppParallel, RcppParallelLibs)

to the NAMESPACE.

[kevinushey]

(this is basically the same hack as the importFrom(Rcpp, evalCpp))

[krlmlr]

Thanks, confirmed.