I got this to work on Linux but it is not working on Windows. *My
understanding is that this should also work on windows, is that correct?*
If so, what should I do? differently?
To get it to work on Linux, I modified my R script as follows:
#' OpenMP Hello World
#'
#' @param nthreads The number of threads that you want to use
#' @example
#' hello(nthreads=2)
#' @export
#' @useDynLib helloOpenMP, .registration = TRUE
hello <- function(nthreads=4) {
(OpenMPController::omp_set_num_threads(nthreads))
.Fortran("hello")
return('Each thread will say hi to you!')
}
> hello(nthreads = 2) Hello from 0
Hello from 1
[1] "Each thread will say hi to you!"
Alas, on Windows the same command just returns "Each thread will say hi to
you!" without the Hello from X
Thanks for your help,
Ignacio
On Sat, Feb 2, 2019 at 11:34 AM Ignacio Martinez <ignaci...@gmail.com>
wrote:
>
>
> I was able to make some progress by using this
> <https://github.com/bert9bert/ParallelForest/blob/master/src/Makevars> as
> a reference. Now:
>
> *This is my makevars:*
> ##### Compiler flags #####
> PKG_FCFLAGS = $(SHLIB_OPENMP_FFLAGS)
> PKG_LIBS = $(SHLIB_OPENMP_CFLAGS)
>
> ##### Phony target for R's build system to invoke #####
> all: $(SHLIB)
>
> ##### Clean target #####
> clean:
> rm -f *.o *.mod
>
> And when I run my hello world function all the threads are used
> regardless of what i specify:
>
> > hello(ncores = 2) Hello from 1
> Hello from 3
> Hello from 0
> Hello from 9
> Hello from 8
> Hello from 2
> Hello from 6
> Hello from 10
> Hello from 11
> Hello from 5
> Hello from 7
> Hello from 4
> $ncores
> [1] 2
>
>
>
> What am I missing? My Fortran subroutine uses !$call
> omp_set_num_threads(ncores) to set the number of threads. Why is this
> not working? How can I fix it?
>
> Thanks a lot for the help
>
> Ignacio
>
>
> On Fri, Feb 1, 2019 at 4:51 PM Ignacio Martinez <ignaci...@gmail.com>
> wrote:
>
>> Hi everybody,
>>
>> I'm trying to develop an R package with Fortran and OpenMP. I wrote a
>> simple hello world but I'm not able to set the number of threads. I found
>> this
>> old email chain
>> <http://r.789695.n4.nabble.com/Set-the-number-of-threads-using-openmp-with-C-td2284685.html>
>> and
>> I tried to set my compile instructions accordingly but i had no luck.
>>
>> *This is my makevars:*
>>
>> PKG_FCFLAGS="-fno-stack-protector"
>> F90FLAGS = "-fopenmp"
>> LDFLAGS = "-fopenmp"
>>
>> *This is my Fortran module:*
>>
>> module hello_openmp
>> use omp_lib
>> implicit none
>> contains
>>
>> subroutine hello(ncores) bind(C, name="hello_")
>> use, intrinsic ::
>> iso_c_binding, only : c_double, c_int
>> integer(c_int), intent(in) :: ncores
>> integer :: iam
>> ! Specify number of threads to use:
>> !$call omp_set_num_threads(ncores)
>> !$omp parallel private(iam)
>> iam=omp_get_thread_num()
>> !$omp critical
>> write(*,*) 'Hello from', iam
>> !$omp end critical
>> !$omp end parallel
>> end subroutine hello
>>
>> end module hello_openmp
>>
>>
>> *and this is my R function:*
>>
>> #'@export
>> #'@useDynLib helloOpenMP, .registration = TRUE
>>
>> hello <- function(ncores=4) {
>> .Fortran("hello", ncores = as.integer(ncores))
>> }
>>
>>
>> *Alas, when I call hello things only run with one thread:*
>>
>> > hello(ncores = 2)$ncores
>> Hello from 0
>> [1] 2
>>
>>
>> Could you point me in the right direction? What am I missing?
>>
>>
>> Thanks,
>>
>>
>> Ignacio
>>
>>
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