add OpenMP version detection and info output

src/info.cpp

@@ -263,7 +263,7 @@ void Info::command(int narg, char **arg)
     fprintf(out,"\nLAMMPS version: %s / %s\n\n",
             universe->version, universe->num_ver);
 
-    char *infobuf = get_os_info();
+    const char *infobuf = get_os_info();
     fprintf(out,"OS information: %s\n\n",infobuf);
     delete[] infobuf;
 
@@ -273,7 +273,7 @@ void Info::command(int narg, char **arg)
     fprintf(out,"sizeof(bigint):   %3d-bit\n",(int)sizeof(bigint)*8);
 
     infobuf = get_compiler_info();
-    fprintf(out,"\nCompiler: %s\n",infobuf);
+    fprintf(out,"\nCompiler: %s with %s\n",infobuf,get_openmp_info());
     delete[] infobuf;
 
     fputs("\nActive compile time flags:\n\n",out);
@@ -1150,6 +1150,39 @@ char *Info::get_compiler_info()
   return buf;
 }
 
+const char *Info::get_openmp_info()
+{
+
+#if !defined(_OPENMP)
+  return (const char *)"OpenMP not enabled";
+#else
+
+// Supported OpenMP version corresponds to the release date of the
+// specifications as posted at https://www.openmp.org/specifications/
+
+#if _OPENMP > 201811
+  return (const char *)"OpenMP newer than v5.0";
+#if _OPENMP == 201811
+  return (const char *)"OpenMP v5.0 or newer";
+#elif _OPENMP == 201511
+  return (const char *)"OpenMP v4.5";
+#elif _OPENMP == 201307
+  return (const char *)"OpenMP v4.0";
+#elif _OPENMP == 201107
+  return (const char *)"OpenMP v3.1";
+#elif _OPENMP == 200805
+  return (const char *)"OpenMP v3.0";
+#elif _OPENMP == 200505
+  return (const char *)"OpenMP v2.5";
+#elif _OPENMP == 200203
+  return (const char *)"OpenMP v2.0";
+#else
+  return (const char *)"unknown OpenMP version";
+#endif
+
+#endif
+}
+
 /* ---------------------------------------------------------------------- */
 
 char **Info::get_variable_names(int &num) {

src/info.h

@@ -42,6 +42,7 @@ class Info : protected Pointers {
 
   static char *get_os_info();
   static char *get_compiler_info();
+  static const char *get_openmp_info();
 
   char **get_variable_names(int &num);
 

src/lammps.cpp

@@ -1087,7 +1087,7 @@ void LAMMPS::print_config(FILE *fp)
   delete[] infobuf;
 
   infobuf = Info::get_compiler_info();
-  fprintf(fp,"Compiler: %s\n\n",infobuf);
+  fprintf(fp,"Compiler: %s with %s\n\n",infobuf,Info::get_openmp_info());
   delete[] infobuf;
 
   fputs("Active compile time flags:\n\n",fp);