Algorithms from the STL are written by C++ experts to be extremely efficient, and they have been around for a long time so they are well tested. In Effective STL, Scott Meyers gives three reasons: efficiency, correctness, and maintainability. It’s generally better to use algorithms from the STL than hand rolled loops. That’s slightly faster than R’s findInterval() function, but is about 1/10 (which uses handwritten C code), we need to compute the calls to. Small note: if we want this function to be as fast as findInterval() in R Upper_bound() we could dereference it to figure out its location, we We can assign into an dereferenced iterator ( out_it) to change the values We step through two iterators (input and output) simultaneously. For more advanced topics, the Effective C++ series by Scott Meyers is a popular choice.ĬppFunction ( 'double sumC(NumericVector x) Many good tutorials and references are freely available, including and. A working knowledge of C++ is helpful, but not essential. We won’t spend much time on advanced features like object-oriented programming or templates because the focus is on writing small, self-contained functions, not big programs. The aim of this chapter is to discuss only those aspects of C++ and Rcpp that are absolutely necessary to help you eliminate bottlenecks in your code. Implementations of many important data structures, from ordered maps to Through the standard template library (STL), C++ has efficient Problems that require advanced data structures and algorithms that R doesn’t The overhead of calling a function in C++ is much lower than in R. Recursive functions, or problems which involve calling functions millions of Loops that can’t be easily vectorised because subsequent iterations depend Typical bottlenecks that C++ can address include:
Rcpp provides a clean, approachable API that lets you write high-performance code, insulated from R’s complex C API. While it is possible to write C or Fortran code for use in R, it will be painful by comparison. Rcpp makes it very simple to connect C++ to R. This magic comes by way of the Rcpp package 117 (with key contributions by Doug Bates, John Chambers, and JJ Allaire).
In this chapter you’ll learn how to improve performance by rewriting key functions in C++. You’ve used profiling to figure out where your bottlenecks are, and you’ve done everything you can in R, but your code still isn’t fast enough.
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