ENH: add convenience handling of "roots" when the slave roots are identical

- a single root entry is interpreted as being the same for all slaves

doc/changes/inotify.txt

@@ -55,15 +55,25 @@ timestamps as before or the (linux-specific) 'inotify' system framework
         - the slave processor directories have no system directory and the
           constant directory only contains the mesh.
     - start the job in distributed mode by specifying the slave roots
-      (so one less than the number of processors) with
-      the -roots command line option:
+      (so one fewer than the number of processors) with
+      the -roots command-line option:
 
-        mpirun -np 2 icoFoam -roots '("/tmp")' -parallel
+        mpirun -np 4 icoFoam -roots '("/tmp" "/tmp" "/tmp")' -parallel
 
     - the alternative to the -roots option is to have a
       cavity/system/decomposeParDict on the master with
             distributed     yes;
-            roots           ("/tmp");
+            roots           ("/tmp" "/tmp" "/tmp");
+
+    - as a convenience for cases when the slave roots are identical,
+      a single root entry is interpreted as being the same for all slaves.
+      With the -roots command-line option, this can take one of two forms:
+
+        mpirun -np 4 icoFoam -roots '("/tmp")' -parallel
+
+      or simply
+
+        mpirun -np 4 icoFoam -roots '"/tmp"' -parallel
 
 
 Details:

src/OpenFOAM/global/argList/argList.C

@@ -549,9 +549,13 @@ Foam::argList::argList
             if (options_.found("roots"))
             {
                 source = "'-roots' option";
-                IStringStream str(options_["roots"]);
-                str >> roots;
-                dictNProcs = roots.size()+1;
+                IStringStream is(options_["roots"]);
+                roots = readList<fileName>(is);
+
+                if (roots.size() != 1)
+                {
+                    dictNProcs = roots.size()+1;
+                }
             }
             else
             {
@@ -579,6 +583,21 @@ Foam::argList::argList
                 }
             }
 
+            // convenience:
+            // when a single root is specified, use it for all processes
+            if (roots.size() == 1)
+            {
+                const fileName rootName(roots[0]);
+                roots.setSize(Pstream::nProcs()-1, rootName);
+
+                // adjust dictNProcs for command-line '-roots' option
+                if (dictNProcs < 0)
+                {
+                    dictNProcs = roots.size()+1;
+                }
+            }
+
+
             // Check number of processors.
             // nProcs     => number of actual procs
             // dictNProcs => number of procs specified in decompositionDict
@@ -602,11 +621,6 @@ Foam::argList::argList
             // distributed data
             if (roots.size())
             {
-                forAll(roots, i)
-                {
-                    roots[i].expand();
-                }
-
                 if (roots.size() != Pstream::nProcs()-1)
                 {
                     FatalError
@@ -617,6 +631,11 @@ Foam::argList::argList
                         << exit(FatalError);
                 }
 
+                forAll(roots, i)
+                {
+                    roots[i].expand();
+                }
+
                 // Distribute the master's argument list (with new root)
                 bool hadCaseOpt = options_.found("case");
                 for
@@ -626,11 +645,7 @@ Foam::argList::argList
                     slave++
                 )
                 {
-                    options_.set
-                    (
-                        "case",
-                        fileName(roots[slave-1])/globalCase_
-                    );
+                    options_.set("case", roots[slave-1]/globalCase_);
 
                     OPstream toSlave(Pstream::scheduled, slave);
                     toSlave << args_ << options_;