# Miscellaneous¶

## Default values for temperature and pressure coupling intervals are now 10¶

With the default mdp input value of -1 for nsttcouple and nstpcouple, grompp would set these values to nstlist. Now these are set to 10 and thus independent of nstlist (note that grompp may choose smaller values when needed for accurate integration).

## Uniform and manual CMake GPU-support configuration¶

The GPU accelerations setup has been changed to be uniform for CUDA and OpenCL. Either option is now enabled by setting GMX_GPU to CUDA or OpenCL in the CMake configuration. To simplify the CMake code, we have also moved away from automated option selection based on the build host. In particular, this means that CUDA will not be enabled unless the GMX_GPU option is explicitly enabled, and CMake will no longer perform the extra steps of trying to detect hardware and propose to install CUDA if hardware is available. Apart from the simplification, this should also make it easier to handle multiple different accelerator APIs targeting e.g. NVIDIA hardware.

## Configuration-time trivalue options changed from autodetection to boolean on/off¶

To simplify the CMake configuration and avoid having multiple settings that change outside of the users direct control we have removed the support for automatically setting booleans. GMX_BUILD_HELP and GMX_HWLOC are now disabled by default, while GMX_LOAD_PLUGINS is enabled by default.

## gmxapi C++ interface¶

gmxapi::Context is now created with gmxapi::createContext(), which allows the client to provide an MPI communicator for the library to use instead of its default (e.g MPI_COMM_WORLD). MPI-enabled clients may use the gmxapi/mpi/gmxapi_mpi.h template header and the assignResource() helper to generate the argument to createContext.

## Unification of several CUDA and OpenCL environment variables¶

The environment variables that had exactly the same meaning in OpenCL and CUDA were unified:

• GMX_CUDA_NB_ANA_EWALD and GMX_OCL_NB_ANA_EWALD into GMX_GPU_NB_ANA_EWALD
• GMX_CUDA_NB_TAB_EWALD and GMX_OCL_NB_TAB_EWALD into GMX_GPU_NB_TAB_EWALD
• GMX_CUDA_NB_EWALD_TWINCUT and GMX_OCL_NB_EWALD_TWINCUT into GMX_GPU_NB_EWALD_TWINCUT

## Dysfunctional parts of the QMMM interface has been removed¶

Currently, GROMACS supports QM/MM officially only via MiMiC; a new CP2K QM/MM interface is being developed within BioExcel. All other QM/MM support has been untested and likely dysfunctional for years and has now been removed from .mdp input and output, resulting in smaller .mdp output files from grompp.