1) force Mac to use gcc (which it refuses to do now) 2) get clang to use omp.h in mac (which from other answers on Stack Overflow, looks impossible) c macos gcc parallel-processing clang. Apple-provided clang does not support OpenMP by default.It is possible to enable the feature in Apple-provided clang and also possible to install a more recent version of clang. Either way, if you want to keep recommending install.packages(., type='mac.binary') in data.table instructions, you need a caveat about how brittle it is. (It also suffers from the well-known internet-proxy issue under RStudio, among many other things).

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The first is a warning about a no longer used variable as of a few days ago since you are installing the latest development version (which is fine): fread.c:64:19: warning: unused variable 'TypeName' [-Wunused-const-variable] static const char TypeName[NUMTYPE][10] That's a correct warning and I'll remove that variable. Pro tools 10. The second is the error: Error in dyn.load(file, DLLpath = DLLpath.): 無法載入共享物件 '/Library/Frameworks/R.framework/Versions/3.3/Resources/library/data.table/libs/datatable.so' ： dlopen(/Library/Frameworks/R.framework/Versions/3.3/Resources/library/data.table/libs/datatable.so, 6): Library not loaded: @rpath/libomp.dylib Referenced from: /Library/Frameworks/R.framework/Versions/3.3/Resources/library/data.table/libs/datatable.so Reason: image not found Other people are finding that too on MacOS and seem to be having some success with the solutions using gcc instead of clang. The problems appears to be clang on MacOS, not data.table. No problems have been reported on Linux or Windows.

It seems the -fopenmp option to clang now causes an error in Apple LLVM 9. > devtools::install_github('Rdatatable/data.table').

A) CRAN only seems to have MacOS binaries up to R 3.2, not 3.3 or 3.4? Options(install.packages.check.source = 'no') install.packages('data.table', type='mac.binary') Warning: unable to access index for repository: cannot open URL ' Warning message: package ‘data.table’ is not available (as a binary package for R version 3.4.2) b) Then I tried manually downloading the binary from and R CMD INSTALL data.table_1.10.4-3.tgz. But it fails on an unresolved dependency on libomp: Loading required package: data.table Error: package or namespace load failed for ‘data.table’ in dyn.load(file, DLLpath = DLLpath.): unable to load shared object '/opt/anaconda3/lib/R/library/data.table/libs/datatable.so': dlopen(/opt/anaconda3/lib/R/library/data.table/libs/datatable.so, 6): Library not loaded: /Library/Frameworks/R.framework/Versions/3.4/Resources/lib/libomp.dylib Referenced from: /opt/anaconda3/lib/R/library/data.table/libs/datatable.so Reason: image not found b2) I do have a /opt/anaconda3/lib/libomp.dylib. Was I supposed to manually supply it in R CMD INSTALL -l., or edit it in into ~/.R/Makevars? B3) libomp has been deprecated from brew, btw.