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# 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.