Merge pull request #1317 from ornladios/adios2-master

USER-ADIOS package with ADIOS 2.x

doc/src/Build_extras.txt

@@ -37,6 +37,7 @@ This is the list of packages that may require additional steps.
 "POEMS"_#poems,
 "PYTHON"_#python,
 "VORONOI"_#voronoi,
+"USER-ADIOS"_#user-adios,
 "USER-ATC"_#user-atc,
 "USER-AWPMD"_#user-awpmd,
 "USER-COLVARS"_#user-colvars,
@@ -572,6 +573,32 @@ the lib/voronoi/Makefile.lammps file.
 
 :line
 
+USER-ADIOS package :h4,link(user-adios)
+
+The USER-ADIOS package requires the "ADIOS I/O library"_https://github.com/ornladios/ADIOS2,
+version 2.3.1 or newer. Make sure that you have ADIOS built either with or
+without MPI to match if you build LAMMPS with or without MPI.
+ADIOS compilation settings for LAMMPS are automatically detected, if the PATH
+and LD_LIBRARY_PATH environment variables have been updated for the local ADIOS
+installation and the instructions below are followed for the respective build systems.
+
+[CMake build]:
+
+-D ADIOS2_DIR=path        # path is where ADIOS 2.x is installed
+-D PKG_USER-ADIOS=yes     :pre
+
+[Traditional make]:
+
+Turn on the USER-ADIOS package before building LAMMPS. If the ADIOS 2.x software is installed in PATH, there is nothing else to do:
+
+make yes-user-adios                       :pre
+
+otherwise, set ADIOS2_DIR environment variable when turning on the package:
+
+ADIOS2_DIR=path make yes-user-adios   # path is where ADIOS 2.x is installed :pre
+
+:line
+
 USER-ATC package :h4,link(user-atc)
 
 The USER-ATC package requires the MANYBODY package also be installed.