Fix typos regarding FindPython3 CMake module hint.

[alexxy/gromacs.git] / docs / release-notes / 2021 / major / portability.rst

diff --git a/docs/release-notes/2021/major/portability.rst b/docs/release-notes/2021/major/portability.rst
index 48bba8a2827bb91f28159758a94f1563561813b5..4c1a22e13eaa4d1b4c0d41d6362f50633c160489 100644 (file)
--- a/docs/release-notes/2021/major/portability.rst
+++ b/docs/release-notes/2021/major/portability.rst
@@ -1,9 +1,69 @@
 Portability
 ^^^^^^^^^^^
 
+Python environment
+""""""""""""""""""
+
+Where Python is required,
+`CPython <https://www.python.org>`__ versions 3.6 to 3.8 are supported.
+
+CMake now detects Python using
+`FindPython3 <https://cmake.org/cmake/help/v3.13/module/FindPython3.html>`__.
+If you previously used ``PYTHON_EXECUTABLE`` to hint the location of the Python
+interpreter, you should instead specify the Python "root" or "prefix" path
+(the directory containing ``./bin/python3``) with CMake variable
+``Python3_ROOT_DIR`` or ``CMAKE_PREFIX_PATH``. As other infrastructure evolves,
+``PYTHON_EXECUTABLE`` may cease to have the desired effect without warning.
+
 .. Note to developers!
    Please use """"""" to underline the individual entries for fixed issues in the subfolders,
    otherwise the formatting on the webpage is messed up.
-   Also, please use the syntax :issue:`number` to reference issues on redmine, without the
+   Also, please use the syntax :issue:`number` to reference issues on GitLab, without the
    a space between the colon and number!
 
+CMake
+"""""
+
+Updated required CMake version to 3.13.
+
+C++ standard
+""""""""""""
+
+|Gromacs| has updated the required C++ standards compliance from C++14 to C++17,
+and requires 2017 standard library features. See the install guide for details.
+
+Cygwin
+""""""
+
+|Gromacs| now builds on Cygwin with both gcc and clang compilers.
+
+Windows
+"""""""
+
+|Gromacs| now builds correctly on Windows with MSVC even when the path
+to the source or build directory has a space in it.
+
+Builds with MSVC 2019 correctly detect the proper static linking setup
+during CMake configuration.
+
+RDTSCP usage and reporting
+""""""""""""""""""""""""""
+
+|Gromacs| now defaults always on x86 to use the RDTSCP machine
+instruction for lower latency timing. Very old machines might need to
+configure with ``GMX_USE_RDTSCP=off``. Non-x86 platforms are
+unaffected, except that they will no longer report that RDTSCP is
+disabled (because that is self-evident).
+
+armv8+sve support (ARM_SVE)
+"""""""""""""""""""""""""""
+Support for ARM Scalable Vector Extensions (SVE) has been added.
+|Gromacs| supports SVE vector length fixed at CMake configure time
+(typically via the -msve-vector-bits=<len> compiler option),
+which is at the time of the release supported in GNU GCC 10 and later,
+and will supported soon by LLVM 12 and compilers based on this.
+The default is to detect the default vector length at CMake configure time,
+and that can be changed with the ``GMX_SIMD_ARM_SVE_LENGTH=<bits>`` option.
+Supported values are 128, 256, 512 and 1024. Note that the nonbonded
+kernels have not been optimized for ARM_SVE as of yet.
+ARM_SVE support is contributed by the Research Organization for Science Information and Technology (RIST)