The second beta release of GROMACS 2016 is available! We are making this available to you to get an early taste of how GROMACS 2016 will look and work, and most importantly to get feedback from you about how well things work. While we try our hardest to keep the quality of GROMACS as high as possible, we’re only human and can get things wrong, and we need your many pairs of eyes to help build a tool that we can all use to do good science! We really need you to test your kinds of simulation on your hardware, both for correctness and performance. This is particularly important if you are using “interesting” hardware or compilers, because we can’t test all of them!
Please do not use this version for doing science you plan to publish – it needs more testing before it’s reliable enough for that. Similarly, please don’t use this version as a base for a project that bundles or forks GROMACS.
What new things can you expect? (See the release notes for more details.)
* the version numbering has changed to be the year of the release, plus (in future) a patch number. GROMACS 2016 will be the initial release from this branch, then GROMACS 2016.1 will have the set of bugs that have been fixed in GROMACS 2016, etc.

* various improvements to simulation performance

* a new SIMD portability layer permitting us to accelerate various minor kernels on the CPU, but also improved use of multi-threading – these will also often improve runs that use accelerators through better load balancing
* improved GPU support (both OpenCL and CUDA), particularly for plain cutoff LJ interactions (10-15% faster), plus other minor improvements
* OpenCL GPU support is now available with all combinations of MPI, thread-MPI and GPU sharing (ie. the same as CUDA)
* SIMD acceleration for POWER8 and ARM64 CPUs
* enhancements to the pull code
Since the first beta, we’ve fixed one major issue with how we used our new random number generator classes, and a collection of minor issues (new and old). See the release notes for details.

Just so you know, a fair bit of the work done since 5.1 has been re-organizational, rather than new features or faster performance. The SIMD support for new kernels has let us run faster across the board with moderate effort, but many of the payoffs are yet to come…

There’s lots of other new things, and old things removed – please see the link to the release notes. All the content of GROMACS 5.1.2 (plus several yet-to-be-released bug fixes) is present, apart from features that have been removed.
If all goes to plan, we hope to ship the final 2016 release in June, but that relies on people joining in and helping us test! We hope you will consider making that contribution, so that we can continue to deliver high-quality free simulation software that will be useful to you on day 1.
You can find the code, manual, release notes, installation instructions and testsuite at the links below.