MathGR is a package for GR calculation, written in Mathematica.
The manual of the package is available at http://arxiv.org/abs/1306.1295
Note: if you download (instead of clone) the package and then unzip, the folder name will include a version number, something like MathGR-0.1.1. Please change it to exactly MathGR before usage. This is because Mathematica requires the folder name to be exactly the same as the package name. Otherwise the packages cannot be properly loaded.