Release 0.16 (2010-08-17)

This release has the following improvements:

• The Nix expression evaluator is now much faster in most cases: typically, 3 to 8 times compared to the old implementation. It also uses less memory. It no longer depends on the ATerm library.

• Support for configurable parallelism inside builders. Build scripts have always had the ability to perform multiple build actions in parallel (for instance, by running make -j 2), but this was not desirable because the number of actions to be performed in parallel was not configurable. Nix now has an option --cores N as well as a configuration setting build-cores = N that causes the environment variable NIX_BUILD_CORES to be set to N when the builder is invoked. The builder can use this at its discretion to perform a parallel build, e.g., by calling make -j N. In Nixpkgs, this can be enabled on a per-package basis by setting the derivation attribute enableParallelBuilding to true.

• nix-store -q now supports XML output through the --xml flag.

• Several bug fixes.