message: split thew subsections Threadin and MPI / OpenCL
diff: @@ -620,17 +620,16 @@ passing interface (MPI).
  different machines. Please refer to
  \url{https://github.com/stan-dev/math/wiki/MPI-Parallelism} for
  more details.
  - \item[OpenCL] in \CmdStan enables Cholesky decompositions to utilize a GPU
  - for large parallel computations. Please refer to
  - \url{https://github.com/stan-dev/math/wiki/OpenCL-GPU-Routines} for setup
  - instructions.
  \end{description}
  %
  The within-chain parallelization for threading and MPI is used in the Stan
  language to parallelize the evaluation of the \Verb|map_rect| command. Note that
  MPI parallelism will take precendence in case both features are
  -enabled. Currently, OpenCL will only pass matrices over to the GPU if their
  -dimensions are larger than 1250x1250.
  +enabled.
  +
  +\subsection{OpenCL}
  +
  +OpenCL in \CmdStan enables Cholesky decompositions to utilize a GPU for large parallel computations. Please refer to \url{https://github.com/stan-dev/math/wiki/OpenCL-GPU-Routines} for setup instructions. Currently, OpenCL will only pass matrices over to the GPU if their dimensions are larger than 1250x1250.
  \section{Optional Components for Developers}
  