rename to LAMMPS_OMP_COMPAT, improve docs

cmake/CMakeLists.txt

@@ -242,9 +242,9 @@ if(BUILD_OMP)
 
   if ((CMAKE_CXX_COMPILER_ID STREQUAL "GNU") AND (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 8.99.9))
     # GCC 9.x strictly implements OpenMP 4.0 semantics for consts.
-    add_definitions(-DLMP_OMP_COMPAT=4)
+    add_definitions(-DLAMMPS_OMP_COMPAT=4)
   else()
-    add_definitions(-DLMP_OMP_COMPAT=3)
+    add_definitions(-DLAMMPS_OMP_COMPAT=3)
   endif()
 endif()
 

cmake/README.md

@@ -264,6 +264,16 @@ cmake -C ../cmake/presets/all_on.cmake -C ../cmake/presets/nolib.cmake -D PKG_GP
   </dl>
   </td>
 </tr>
+<tr>
+  <td><code>LAMMPS_OMP_COMPAT</code></td>
+  <td>Workaround for backwards-incompatible changes regarding predetermined sharing modes in OpenMP 4.x.  A value of 3 or 4 should be used, reflecting the version of the OpenMP spec that is implemented by the compiler.</td>
+  <td>
+  <dl>
+    <dt><code>3</code> (default except for known OMP 4.0 compilers)</dt>
+    <dt><code>4</code></dt>
+  </dl>
+  </td>
+</tr>
 <tr>
   <td><code>LAMMPS_MEMALIGN</code></td>
   <td>controls the alignment of blocks of memory allocated by LAMMPS</td>

doc/src/Build_basics.rst

@@ -147,7 +147,8 @@ semantics, which are incompatible with the OpenMP 3.1 semantics used
 in LAMMPS (for maximal compatibility with compiler versions in use).
 LAMMPS will try to detect compilers that use OpenMP 4.0 semantics and
 change the directives accordingly, but if your compiler is not
-detected, you may set the CMake variable ``-D LMP_OMP_COMPAT=4``.
+detected, you may set the define ``-D LAMMPS_OMP_COMPAT=4`` in ``LMP_INC``
+or the CMake build command.
 
 ----------
 

src/omp_compat.h

@@ -25,7 +25,7 @@
 // so this is what LAMMPS primarily uses.  For those compilers
 // that strictly implement OpenMP 4.0 (such as GCC 9.0), we
 // give up default(none).
-#if LMP_OMP_COMPAT == 4
+#if LAMMPS_OMP_COMPAT == 4
 #    define LMP_SHARED(...)
 #    define LMP_DEFAULT_NONE default(shared)
 #else