ENH: improve handling of pt-scotch headers/libraries

- provide dedicated detection 'have_ptscotch' function that can be
  used after the 'have_scotch' function.

  It sets the PTSCOTCH_ARCH_PATH, PTSCOTCH_INC_DIR, PTSCOTCH_LIB_DIR
  and helps when the serial and parallel versions are located with
  different logic.

src/parallel/decompose/Allwmake

@@ -41,7 +41,8 @@ wmakeLnInclude -u decompositionMethods
 if have_scotch
 then
     wmake $targetType scotchDecomp
-    if [ -d "$FOAM_LIBBIN/$FOAM_MPI" ]
+
+    if have_ptscotch
     then
         wmakeMpiLib "$SCOTCH_VERSION" ptscotchDecomp
     fi

src/parallel/decompose/ptscotchDecomp/Make/options

 /*
- * NB: mplib PINC must appear after the SCOTCH_ARCH_PATH/include/FOAM_MPI
- * to ensure we do not accidentally get a ptscotch header from the
- * mpi distribution.
+ * NB: mplib PINC must appear after PTSCOTCH_INC_DIR to ensure we
+ * do not accidentally get a ptscotch header from the MPI distribution.
  */
 sinclude $(GENERAL_RULES)/mplib$(WM_MPLIB)
 sinclude $(DEFAULT_RULES)/mplib$(WM_MPLIB)
 
 EXE_INC = \
-    -I$(SCOTCH_ARCH_PATH)/include/$(FOAM_MPI) \
+    -I$(PTSCOTCH_INC_DIR) \
     -I$(SCOTCH_INC_DIR) \
     $(PFLAGS) $(PINC) \
     -I../decompositionMethods/lnInclude
@@ -17,9 +16,8 @@ EXE_INC = \
  * ptscotch 6 requires scotch linked in, but does not declare the dependency
  */
 LIB_LIBS = \
+    -L$(PTSCOTCH_LIB_DIR) \
     -L$(SCOTCH_LIB_DIR) \
-    -L$(FOAM_EXT_LIBBIN)/$(FOAM_MPI) \
-    -L$(FOAM_EXT_LIBBIN) \
     -lptscotch -lptscotcherrexit \
     -lscotch
 

wmake/scripts/have_scotch

@@ -37,6 +37,7 @@ no_scotch()
 {
     unset HAVE_SCOTCH SCOTCH_ARCH_PATH SCOTCH_INC_DIR SCOTCH_LIB_DIR
     unset SCOTCH_VERSION
+    unset HAVE_PTSCOTCH PTSCOTCH_ARCH_PATH PTSCOTCH_INC_DIR PTSCOTCH_LIB_DIR
     return 0
 }
 
@@ -48,6 +49,11 @@ echo_scotch()
     echo "root=$SCOTCH_ARCH_PATH"
     echo "include=$SCOTCH_INC_DIR"
     echo "library=$SCOTCH_LIB_DIR"
+    echo
+    echo "ptscotch=${HAVE_PTSCOTCH:-false}"
+    echo "root=$PTSCOTCH_ARCH_PATH"
+    echo "include=$PTSCOTCH_INC_DIR"
+    echo "library=$PTSCOTCH_LIB_DIR"
 }
 
 
@@ -177,13 +183,105 @@ have_scotch()
 }
 
 
+# Must be called after have_scotch!
+#
+# On success, return 0 and export variables
+# -> HAVE_PTSCOTCH, PTSCOTCH_ARCH_PATH, PTSCOTCH_INC_DIR, PTSCOTCH_LIB_DIR
+have_ptscotch()
+{
+    local prefix header library static settings warn
+    warn="==> skip ptscotch"
+
+    if [ "$HAVE_SCOTCH" != true ]
+    then
+        echo "$warn (no serial scotch available?)"
+        return 1
+    fi
+
+    # Reuse old settings
+    [ -n "$PTSCOTCH_ARCH_PATH" ] || PTSCOTCH_ARCH_PATH="$SCOTCH_ARCH_PATH"
+
+    # Location
+    prefix="$PTSCOTCH_ARCH_PATH"
+
+    # Header/library names
+    header="ptscotch.h"
+    library="libptscotch$extLibso"
+    static="libptscotch$extLiba"
+
+    # ----------------------------------
+    if isNone "$prefix"
+    then
+        [ -n "$warn" ] && echo "$warn (disabled)"
+        return 1
+    elif hasAbsdir "$prefix"
+    then
+        header=$(findFirstFile  \
+            "$prefix/include/$FOAM_MPI/$header" \
+            "$prefix/include/$header"
+        )
+
+        library=$(findFirstFile \
+            "$(thirdExtLib $FOAM_MPI/$library)" \
+            "$(thirdExtLib $library)" \
+            "$prefix/lib/$static" \
+            "$prefix/lib/$library" \
+            "$prefix/lib$WM_COMPILER_LIB_ARCH/$static" \
+            "$prefix/lib$WM_COMPILER_LIB_ARCH/$library" \
+        )
+
+    elif isSystem "$prefix"
+    then
+        prefix=/usr
+
+        header=$(findFirstFile \
+            "/usr/local/include/ptscotch/$header" \
+            "/usr/local/include/scotch/$header" \
+            "/usr/local/include/$header" \
+            "/usr/include/ptscotch/$header" \
+            "/usr/include/scotch/$header" \
+            "/usr/include/$header" \
+        )
+
+        case "$header" in (/usr/local/*) prefix=/usr/local ;; esac
+
+        library=$(findFirstFile \
+            "$prefix/lib/$library" \
+            "$prefix/lib$WM_COMPILER_LIB_ARCH/$library" \
+        )
+    else
+        unset prefix header library
+    fi
+    # ----------------------------------
+
+    # Header found?
+    [ -n "$header" ] || {
+        [ -n "$warn" ] && echo "$warn (no header)"
+        return 2
+    }
+
+    # Library found?
+    [ -n "$library" ] || {
+        [ -n "$warn" ] && echo "$warn (no library)"
+        return 2
+    }
+
+    # OK
+    echo "ptscotch - $prefix"
+    export HAVE_PTSCOTCH=true
+    export PTSCOTCH_ARCH_PATH="$prefix"
+    export PTSCOTCH_INC_DIR="${header%/*}"     # Basename
+    export PTSCOTCH_LIB_DIR="${library%/*}"    # Basename
+}
+
+
 # Force reset of old variables
 no_scotch
 
 # Testing
 if [ "$1" = "-test" ]
 then
-    have_scotch
+    have_scotch && have_ptscotch
     echo_scotch
 fi
 

wmake/scripts/sysFunctions

@@ -48,14 +48,20 @@ then
     esac
 
 
-    # True if OS is Darwin.
-    # Uses libso extension to cache the value
-    # (instead of calling 'uname -s' each time)
+    # True if target OS is Darwin.
+    # Uses cached value from libso extension
     isDarwin()
     {
         test "$extLibso" = ".dylib"
     }
 
+    # True if target OS is Windows
+    # Uses cached value from libso extension
+    isWindows()
+    {
+        test "$extLibso" = ".dll"
+    }
+
 
     # True if '$1' begins with '/'
     isAbsdir()