This project is used to compile openblas on Windows so that it can be used as a faster BLAS alternative to the default BLAS provided with R on Windows.

This is used in the companion r-openblas tools--an openblas optimized 64-bit R for Windows.

First, I am grateful to Avraham Adler for his excellent blog post covering this topic. If you want to read his script--which this package mostly follows--please do so.

Prerequisites:

The key difficultly in getting this to work is R is built using the GNU tools which have sometimes spotty and confusing windows support. However, the key elemenets are that you need to download the following:

• Rtools Used for the actual gcc and gfortran compilers.
• MSYS2 The compilation environment. MSYS2 bash must be used.

- Appveyor Is an online continuous integration system that essentially runs Windows buils.

Strategy:

GCC can be configured either through a Makefile or using environment variables. In this example, I'll use environment variables to avoid having to copy files around. We can configured the environment variables using an appveyor.yml file.

GNU make needs to be run from within a bash shell environment. However, it is very important to use the gcc and gfortran that are shipped with Rtools. Typically in Windows GUI this could be accomplished by opening an MSYS2 shell, running export PATH=\C\Rtools\bin:\C\Rtools\mingw_64\bin:$PATH, then make all. This project accomplish the same thing using a bash script.

Once this is completed, the compiled library is avaiable as a downloadable Artifact from Appveyor. Go to the project's Appveyor site:

https://ci.appveyor.com/project/thequackdaddy/openblasr

Currently, I we are only building drivers for Intel's Haswell, Sandybridge, and Nehalem architectures. Others could be easily added by just adding to the appveyor.yml file.

Pick the most recent build that succeeded and select the Artifact tab to download it.