I was inspired by the fst package to try to write a C++ function to quickly serialize some data structures I have in R to disk.

## Why is this naive matrix multiplication faster than base R's?

In R, matrix multiplication is very optimized, i.e. is really just a call to BLAS/LAPACK. However, I'm surprised this very naive C++ code for matrix multiplication seems reliably 30% faster.

## STL random_shuffle generates highly correlated sequences

Notice the accepted answer pointed out the problem lies in reseeding. Reseeding is not the reason. Tests without reseeding also resulted in high correlations before posting. See Note1.

## Deciding between NumericVector and arma::vec in Rcpp

With RcppArmadillo the conversion from R to Rcpp with arma::vec is just as easy as with Rcpp and NumericVector. My project utilizes RcppArmadillo.