rename and document script to automatically convert 'default(none)' to...

compilers it is -qopenmp.  If you are using a different compiler,

please refer to its documentation.

[OpenMP Compiler compatibility info]: :link(default-none-issues)

Some compilers do not fully support the 'default(none)' directive

and others (e.g. GCC version 9 and beyond) may implement OpenMP 4.0

semantics, which are incompatible with the OpenMP 3.1 directives used

in LAMMPS (for maximal compatibility with compiler versions in use).

In those case, all 'default(none)' directives (which aid in detecting

incorrect and unwanted sharing) can be replaced with 'default(shared)'

while dropping all 'shared()' directives. The script

'src/USER-OMP/hack_openmp_for_pgi_gcc9.sh' can be used to automate

this conversion.

:line

Choice of compiler and compile/link options :h4,link(compile)

LINKFLAGS: -qopenmp             # for Intel compilers on Linux :pre

For other platforms and compilers, please consult the documentation

about OpenMP support for your compiler.

about OpenMP support for your compiler. Please see the note about

how to address compatibility "issues with the 'default(none)'

directive"_Build_basics.html#default-none-issues of some compilers.

:line

#!/bin/sh

# convert default(none) directives for OpenMP pragmas to default(shared) and remove shared() directive

# this allows compiling OpenMP pragmas in LAMMPS with compilers that don't support default(none) properly

# or require backward incompatible OpenMP 4 and OpenMP 5 semantics

for f in *.h *.cpp

do \

   sed -e '/#pragma omp/s/^\(.*default\)(none)\(.*\)$/\1(shared)\2/' \