README.Rmd

---
title: "Strider"
author: "Timothy H. Keitt"
date: "`r Sys.Date()`"
output: github_document
---

"I don't think he knows about second breakfast" - Meriadoc 'Merry' Brandybuck

Adapting multidimensional legacy buffers to the C++ standard library is difficult owing to a lack of strided (address-skipping) iterators. **Strider** provides an address-skipping pointer adapter. It can be used to scan multidimensional data along any desired margin using the standard library algorithms.

This code snippet computes row sums of a matrix.

```{Rcpp eval=FALSE}
  for_each(make_strided(begin(x), nr), make_strided(end(x)), [&](const double& y) {
    transform(&y, &y + nr, begin(res), begin(res), plus<double>()); });
```

It is cache and compiler friendly and runs nearly four times faster than R's built-in ```rowSums``` function. See [the vignette](https://thk686.github.io/strider/articles/strider.html) for details.

[The header file](https://github.com/thk686/strider/blob/master/inst/include/strider.h) is stand-alone and can be used separate from [R](https://www.r-project.org). It relies on the [Boost iterator library](https://www.boost.org/doc/libs/release/libs/iterator/).

#### Installation

```
devtools::install_github("thk686/strider")
```

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