[Rd] How to safely using OpenMP pragma inside a .C() function?

[pawelm]

I just found this (performance improvement of the "dist" function when using
openmp):

.Internal(setMaxNumMathThreads(1)); .Internal(setNumMathThreads(1)); m <-
matrix(rnorm(810000),900,900); system.time(d <- dist(m))

  user  system elapsed 
  3.510   0.013   3.524 

.Internal(setMaxNumMathThreads(5)); .Internal(setNumMathThreads(5)); m <-
matrix(rnorm(810000),900,900); system.time(d <- dist(m));

   user  system elapsed 
  3.536   0.007   1.321 

Works great! Just the question stays if it's a good practice to use
"R_num_math_threads" in external packages?

Thanks

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