ENH: provide openmp compile and link flags.

- the USE_OMP preprocessor symbol is also defined with the openmp
  compile flag to allow conditional compilation of openmp-specific
  code.

applications/test/openmp/Make/files

+Test-openmp.C
+
+EXE = $(FOAM_USER_APPBIN)/Test-openmp

applications/test/openmp/Make/options

+EXE_INC = ${COMP_OPENMP}
+
+/* Mostly do not need to explicitly link openmp libraries */
+/* EXE_LIBS = ${LINK_OPENMP} */

applications/test/openmp/Test-openmp.C

+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2017 OpenCFD Ltd.
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Description
+    Simple test program for compiling/running openmp
+
+\*---------------------------------------------------------------------------*/
+
+#include <cstdio>
+#include <cstdlib>
+#include <iostream>
+
+#ifdef USE_OMP
+#include <omp.h>
+#endif
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+// Main program:
+
+int main(int argc, char *argv[])
+{
+    int nThreads, threadId;
+
+// Fork threads with their own copies of variables
+#ifdef USE_OMP
+#pragma omp parallel private(nThreads, threadId)
+    {
+        threadId = omp_get_thread_num();
+        nThreads = omp_get_num_threads();
+
+        // Printf rather than cout to ensure that it emits in one go
+        printf("Called from thread = %d\n", threadId);
+
+        // Master thread
+        if (threadId == 0)
+        {
+            // Printf rather than cout to ensure that it emits in one go
+            printf("Number of threads = %d\n", nThreads);
+        }
+    }
+#else
+    std::cout << "Compiled without openmp!\n";
+#endif
+
+    return 0;
+}
+
+
+// ************************************************************************* //

etc/config.sh/kahip

@@ -42,18 +42,11 @@
 #     An Int64 OpenFOAM version can use it, but the mesh size is limited
 #     accordingly.
 #
-#     If KaHIP was compiled with openmp, you may need additional
-#     compile or link flags in KAHIP_COMP_FLAGS KAHIP_LINK_FLAGS
-#
 #------------------------------------------------------------------------------
 # USER EDITABLE PART: Changes made here may be lost with the next upgrade
 
 KAHIP_VERSION=kahip-2.00
 export KAHIP_ARCH_PATH=$WM_THIRD_PARTY_DIR/platforms/$WM_ARCH$WM_COMPILER/$KAHIP_VERSION
 
-# Adjust as required
-# export KAHIP_COMP_FLAGS="-fopenmp"
-export KAHIP_LINK_FLAGS="-lgomp"
-
 # END OF (NORMAL) USER EDITABLE PART
 #------------------------------------------------------------------------------

src/parallel/decompose/Allwmake

@@ -33,7 +33,6 @@ hasKahip()
     local header label settings
 
     unset KAHIP_ARCH_PATH KAHIP_VERSION
-    unset KAHIP_COMP_FLAGS KAHIP_LINK_FLAGS
     settings=$($WM_PROJECT_DIR/bin/foamEtcFile config.sh/kahip) || {
         echo "$warning (no config.sh/kahip settings)"
         return 1

src/parallel/decompose/kahipDecomp/Make/options

 EXE_INC = \
     -I$(KAHIP_ARCH_PATH)/include \
-    -I../decompositionMethods/lnInclude \
-    $(KAHIP_COMP_FLAGS)
+    -I../decompositionMethods/lnInclude
 
 /*
  * The $(KAHIP_ARCH_PATH)/lib$WM_COMPILER_LIB_ARCH path is provided
- * to support central, non-thirdparty installations
+ * to support central, non-thirdparty installations.
+ *
+ * KaHIP is often compiled with openmp, but may be missing the
+ * link dependency for openmp.
  */
 LIB_LIBS = \
     -L$(KAHIP_ARCH_PATH)/lib \
     -L$(KAHIP_ARCH_PATH)/lib$(WM_COMPILER_LIB_ARCH) \
-    -L$(FOAM_EXT_LIBBIN) $(KAHIP_LINK_FLAGS) -lkahip
+    -L$(FOAM_EXT_LIBBIN) $(LINK_OPENMP) -lkahip

wmake/rules/linux64Clang/general

@@ -4,5 +4,6 @@ PROJECT_LIBS = -l$(WM_PROJECT) -ldl
 
 include $(GENERAL_RULES)/standard
 
+include $(DEFAULT_RULES)/openmp
 include $(DEFAULT_RULES)/c
 include $(DEFAULT_RULES)/c++

wmake/rules/linux64Clang/openmp

+# Flags for compiling/linking openmp
+
+COMP_OPENMP = -DUSE_OMP -fopenmp
+LINK_OPENMP = -lgomp

wmake/rules/linux64Gcc/general

@@ -4,5 +4,6 @@ PROJECT_LIBS = -l$(WM_PROJECT) -ldl
 
 include $(GENERAL_RULES)/standard
 
+include $(DEFAULT_RULES)/openmp
 include $(DEFAULT_RULES)/c
 include $(DEFAULT_RULES)/c++

wmake/rules/linux64Gcc/openmp

+# Flags for compiling/linking openmp
+
+COMP_OPENMP = -DUSE_OMP -fopenmp
+LINK_OPENMP = -lgomp

wmake/rules/linux64GccKNL/general

@@ -4,5 +4,6 @@ PROJECT_LIBS = -l$(WM_PROJECT) -ldl
 
 include $(GENERAL_RULES)/standard
 
+include $(DEFAULT_RULES)/openmp
 include $(DEFAULT_RULES)/c
 include $(DEFAULT_RULES)/c++

wmake/rules/linux64GccKNL/openmp

+# Flags for compiling/linking openmp
+
+COMP_OPENMP = -DUSE_OMP -fopenmp
+LINK_OPENMP = -lgomp

wmake/rules/linux64Icc/general

@@ -4,5 +4,6 @@ PROJECT_LIBS = -l$(WM_PROJECT) -ldl
 
 include $(GENERAL_RULES)/standard
 
+include $(DEFAULT_RULES)/openmp
 include $(DEFAULT_RULES)/c
 include $(DEFAULT_RULES)/c++

wmake/rules/linux64Icc/openmp

+# Flags for compiling/linking openmp
+
+COMP_OPENMP = -DUSE_OMP -qopenmp
+LINK_OPENMP = -liomp5

wmake/rules/linux64IccKNL/openmp

+# Flags for compiling/linking openmp
+
+COMP_OPENMP = -DUSE_OMP -qopenmp
+LINK_OPENMP = -liomp5

wmake/rules/linuxARM7Gcc/general

@@ -5,5 +5,6 @@ PROJECT_LIBS = -l$(WM_PROJECT) -ldl
 
 include $(GENERAL_RULES)/standard
 
+include $(DEFAULT_RULES)/openmp
 include $(DEFAULT_RULES)/c
 include $(DEFAULT_RULES)/c++

wmake/rules/linuxARM7Gcc/openmp

+# Flags for compiling/linking openmp
+
+COMP_OPENMP = -DUSE_OMP -fopenmp
+LINK_OPENMP = -lgomp

wmake/rules/linuxClang/general

@@ -5,5 +5,6 @@ PROJECT_LIBS = -l$(WM_PROJECT) -ldl
 
 include $(GENERAL_RULES)/standard
 
+include $(DEFAULT_RULES)/openmp
 include $(DEFAULT_RULES)/c
 include $(DEFAULT_RULES)/c++

wmake/rules/linuxClang/openmp

+# Flags for compiling/linking openmp
+
+COMP_OPENMP = -DUSE_OMP -fopenmp
+LINK_OPENMP = -lgomp

wmake/rules/linuxGcc/general

@@ -5,5 +5,6 @@ PROJECT_LIBS = -l$(WM_PROJECT) -ldl
 
 include $(GENERAL_RULES)/standard
 
+include $(DEFAULT_RULES)/openmp
 include $(DEFAULT_RULES)/c
 include $(DEFAULT_RULES)/c++