ENH: reduce startup time for foamToVTK conversion

- Similar to ensight converters (issue #240),
  improve speed for detection of lagrangian clouds.

- provide a -noLagrangian option for symmetry

applications/utilities/postProcessing/dataConversion/foamToVTK/findClouds.H

@@ -0,0 +1,71 @@
+// check all time directories for the following:
+
+// Any cloud names:
+HashSet<fileName> allCloudDirs;
+
+if (timeDirs.size() && !noLagrangian)
+{
+    const fileName& baseDir = mesh.time().path();
+    const fileName& cloudPrefix = regionPrefix/cloud::prefix;
+
+    Info<< "Searching for lagrangian ... " << flush;
+
+    forAll(timeDirs, timeI)
+    {
+        const word& timeName = timeDirs[timeI].name();
+
+        // DO NOT USE -->>  runTime.setTime(timeDirs[timeI], timeI);  <<--
+        // It incurs a large overhead when done so frequently.
+
+        fileNameList cloudDirs = readDir
+        (
+            baseDir/timeName/cloudPrefix,
+            fileName::DIRECTORY
+        );
+
+        forAll(cloudDirs, cloudI)
+        {
+            const word& cloudName = cloudDirs[cloudI];
+
+            IOobjectList cloudObjs
+            (
+                mesh,
+                timeName,
+                cloudPrefix/cloudName
+            );
+
+            // clouds always require "positions"
+            if (cloudObjs.found("positions"))
+            {
+                if (allCloudDirs.insert(cloudName))
+                {
+                    Info<< "At time: " << timeName
+                        << " detected cloud directory : " << cloudName
+                        << endl;
+                }
+            }
+        }
+    }
+
+    if (allCloudDirs.empty())
+    {
+        Info<< "none detected." << endl;
+    }
+}
+
+// sorted list of cloud names
+const fileNameList cloudNames(allCloudDirs.sortedToc());
+
+if (cloudNames.size())
+{
+    // complete the echo information
+    Info<< "(";
+    forAll(cloudNames, cloudNo)
+    {
+        Info<< ' ' << cloudNames[cloudNo];
+    }
+    Info<< " ) " << endl;
+}
+
+
+// ************************************************************************* //

applications/utilities/postProcessing/dataConversion/foamToVTK/foamToVTK.C

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2016 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -71,6 +71,9 @@ Usage
     \param -noInternal \n
     Do not generate file for mesh, only for patches
 
+    \param -noLagrangian \n
+    Suppress writing lagrangian positions and fields.
+
     \param -noPointValues \n
     No pointFields
 
@@ -290,6 +293,12 @@ int main(int argc, char *argv[])
         "noInternal",
         "do not generate file for mesh, only for patches"
     );
+    argList::addBoolOption
+    (
+        "noLagrangian",
+        "suppress writing lagrangian positions and fields"
+    );
+
     argList::addBoolOption
     (
         "noPointValues",
@@ -336,6 +345,7 @@ int main(int argc, char *argv[])
     const bool doLinks         = !args.optionFound("noLinks");
     bool binary                = !args.optionFound("ascii");
     const bool useTimeName     = args.optionFound("useTimeName");
+    const bool noLagrangian    = args.optionFound("noLagrangian");
 
     // Decomposition of polyhedral cells into tets/pyramids cells
     vtkTopo::decomposePoly     = !args.optionFound("poly");
@@ -406,9 +416,9 @@ int main(int argc, char *argv[])
 
     // VTK/ directory in the case
     fileName fvPath(runTime.path()/"VTK");
-    // Directory of mesh (region0 gets filtered out)
-    fileName regionPrefix = "";
 
+    // Directory of mesh (region0 gets filtered out)
+    fileName regionPrefix;
     if (regionName != polyMesh::defaultRegion)
     {
         fvPath = fvPath/regionName;
@@ -446,43 +456,7 @@ int main(int argc, char *argv[])
         << timer.cpuTimeIncrement() << " s, "
         << mem.update().size() << " kB" << endl;
 
-
+    #include "findClouds.H"
-    // Scan for all possible lagrangian clouds
-    HashSet<fileName> allCloudDirs;
-    forAll(timeDirs, timeI)
-    {
-        runTime.setTime(timeDirs[timeI], timeI);
-        fileNameList cloudDirs
-        (
-            readDir
-            (
-                runTime.timePath()/regionPrefix/cloud::prefix,
-                fileName::DIRECTORY
-            )
-        );
-        forAll(cloudDirs, i)
-        {
-            IOobjectList sprayObjs
-            (
-                mesh,
-                runTime.timeName(),
-                cloud::prefix/cloudDirs[i]
-            );
-
-            IOobject* positionsPtr = sprayObjs.lookup(word("positions"));
-
-            if (positionsPtr)
-            {
-                if (allCloudDirs.insert(cloudDirs[i]))
-                {
-                    Info<< "At time: " << runTime.timeName()
-                        << " detected cloud directory : " << cloudDirs[i]
-                        << endl;
-                }
-            }
-        }
-    }
-
 
     forAll(timeDirs, timeI)
     {
@@ -490,7 +464,7 @@ int main(int argc, char *argv[])
 
         Info<< "Time: " << runTime.timeName() << endl;
 
-        word timeDesc =
+        const word timeDesc =
             useTimeName ? runTime.timeName() : Foam::name(runTime.timeIndex());
 
         // Check for new polyMesh/ and update mesh, fvMeshSubset and cell
@@ -662,7 +636,7 @@ int main(int argc, char *argv[])
               + dtf.size();
 
 
-        // Construct pointMesh only if nessecary since constructs edge
+        // Construct pointMesh only if necessary since constructs edge
         // addressing (expensive on polyhedral meshes)
         if (noPointValues)
         {
@@ -1149,9 +1123,9 @@ int main(int argc, char *argv[])
         //
         //---------------------------------------------------------------------
 
-        forAllConstIter(HashSet<fileName>, allCloudDirs, iter)
+        forAll(cloudNames, cloudNo)
         {
-            const fileName& cloudName = iter.key();
+            const fileName& cloudName = cloudNames[cloudNo];
 
             // Always create the cloud directory.
             mkDir(fvPath/cloud::prefix/cloudName);
@@ -1172,9 +1146,7 @@ int main(int argc, char *argv[])
                 cloud::prefix/cloudName
             );
 
-            IOobject* positionsPtr = sprayObjs.lookup(word("positions"));
+            if (sprayObjs.found("positions"))
-
-            if (positionsPtr)
             {
                 wordList labelNames(sprayObjs.names(labelIOField::typeName));
                 Info<< "        labels            :";