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- resolve in favour of "inline explicit", which had marginally more
  uses and provides consistent prefixing for inline methods.

- make the purpose more explicit, and reduces some work for the
  compiler as well.

- use refCount instead of the tmp<...>::refCount alias

- The iterator for a HashSet dereferences directly to its key.

- Eg,

      for (const label patchi : patchSet)
      {
          ...
      }
  vs.
      forAllConstIter(labelHashSet, patchSet, iter)
      {
          const label patchi = iter.key();
          ...
      }

- IOstreamOption class to encapsulate format, compression, version.
  This is ordered to avoid internal padding in the structure, which
  reduces several bytes of memory overhead for stream objects
  and other things using this combination of data.

  Byte-sizes:
      old  IOstream:48  PstreamBuffers:88  Time:928
      new  IOstream:24  PstreamBuffers:72  Time:904

====

STYLE: remove support for deprecated uncompressed/compressed selectors

In older versions, the system/controlDict used these types of
specifications:

    writeCompression uncompressed;
    writeCompression compressed;

As of DEC-2009, these were deprecated in favour of using normal switch
names:

    writeCompression true;
    writeCompression false;
    writeCompression on;
    writeCompression off;

Now removed these deprecated names and treat like any other unknown
input and issue a warning. Eg,

   Unknown compression specifier 'compressed', assuming no compression

====

STYLE: provide Enum of stream format names (ascii, binary)

====

COMP: fixed incorrect IFstream construct in FIREMeshReader

- spurious bool argument (presumably meant as uncompressed) was being
  implicitly converted to a versionNumber. Now caught by making
  IOstreamOption::versionNumber constructor explicit.

- bad version specifier in changeDictionary

- specialize transfer and swap to ensure allocated capacity isn't
  forgotten.

- can assist the compiler in producing tighter code.

- when constructing dimensioned fields that are to be zero-initialized,
  it is preferrable to use a form such as

      dimensionedScalar(dims, Zero)
      dimensionedVector(dims, Zero)

  rather than

      dimensionedScalar("0", dims, 0)
      dimensionedVector("zero", dims, vector::zero)

  This reduces clutter and also avoids any suggestion that the name of
  the dimensioned quantity has any influence on the field's name.

  An even shorter version is possible. Eg,

      dimensionedScalar(dims)

  but reduces the clarity of meaning.

- NB: UniformDimensionedField is an exception to these style changes
  since it does use the name of the dimensioned type (instead of the
  regIOobject).

This class is largely a pre-C++11 holdover. It is now possible to
simply use move construct/assignment directly.

In a few rare cases (eg, polyMesh::resetPrimitives) it has been
replaced by an autoPtr.

Improve alignment of its behaviour with std::shared_ptr

  - element_type typedef
  - swap, reset methods

* additional reference access methods:

cref()
    returns a const reference, synonymous with operator().
    This provides a more verbose alternative to using the '()' operator
    when that is desired.

        Mnemonic: a const form of 'ref()'

constCast()
    returns a non-const reference, regardless if the underlying object
    itself is a managed pointer or a const object.
    This is similar to ref(), but more permissive.

        Mnemonic: const_cast<>

    Using the constCast() method greatly reduces the amount of typing
    and reading. And since the data type is already defined via the tmp
    template parameter, the type deduction is automatically known.

    Previously,

        const tmp<volScalarField>& tfld;

        const_cast<volScalarField&>(tfld()).rename("name");
        volScalarField& fld = const_cast<volScalarField&>(tfld());

    Now,

        tfld.constCast().rename("name");
        auto& fld = tfld.constCast();

--

BUG: attempts to move tmp value that may still be shared.

- old code simply checked isTmp() to decide if the contents could be
  transfered. However, this means that the content of a shared tmp
  would be removed, leaving other instances without content.

* movable() method checks that for a non-null temporary that is
  unique (not shared).

Improve alignment of its behaviour with std::unique_ptr

  - element_type typedef
  - release() method - identical to ptr() method
  - get() method to get the pointer without checking and without releasing it.
  - operator*() for dereferencing

Method name changes

  - renamed rawPtr() to get()
  - renamed rawRef() to ref(), removed unused const version.

Removed methods/operators

  - assignment from a raw pointer was deleted (was rarely used).
    Can be convenient, but uncontrolled and potentially unsafe.
    Do allow assignment from a literal nullptr though, since this
    can never leak (and also corresponds to the unique_ptr API).

Additional methods

  - clone() method: forwards to the clone() method of the underlying
    data object with argument forwarding.

  - reset(autoPtr&&) as an alternative to operator=(autoPtr&&)

STYLE: avoid implicit conversion from autoPtr to object type in many places

- existing implementation has the following:

     operator const T&() const { return operator*(); }

  which means that the following code works:

       autoPtr<mapPolyMesh> map = ...;
       updateMesh(*map);    // OK: explicit dereferencing
       updateMesh(map());   // OK: explicit dereferencing
       updateMesh(map);     // OK: implicit dereferencing

  for clarity it may preferable to avoid the implicit dereferencing

- prefer operator* to operator() when deferenced a return value
  so it is clearer that a pointer is involve and not a function call
  etc    Eg,   return *meshPtr_;  vs.  return meshPtr_();

- the wordHashSet typedef is always available when HashSet has been
  included.

- use default HashTable key (word) instead of explicitly mentioning it

- support move construct/assignment for linked-lists themselves
  and when moving into a 'normal' list

- better consistency with begin/end signatures and the various
  iterators.

- for indirect linked-lists, provide iterator access to the underlying
  data element address:   iter.get()  vs  &(iter())

- add standard '->' indirection for iterators (as per normal STL
  definitions)

- makes for clearer code

ENH: make writeIfDifferent part of Ostream

- in most cases already checked valid() so don't need additional check
  for setting an existing pointer

- makes it accessible for containers that manage their own storage
  and derive directly from UList.

- DynamicList::min_size() method to access the corresponding
  SizeMin template parameter.

- ensure consistency in the reserve size for the constructor

      DynamicList<..> lst(N);

  now has identical sizing as

      DynamicList<..> lst();
      reserve(N);

- now use public functions instead of direct access of private 'capacity_'
  information

- improve functional compatibility with DynList (remove methods)
  * eg, remove an element from any position in a DynamicList
  * reduce the number of template parameters
  * remove/subset regions of DynamicList

- propagate Swap template specializations for lists, hashtables

- move construct/assignment to various containers.

- add find/found methods for FixedList and UList for a more succinct
  (and clearer?) usage than the equivalent global findIndex() function.

- simplify List_FOR_ALL loops

Henry Weller authored Jun 26, 2017 and Andrew Heather committed Jun 26, 2017

for consistency with reactingTwoPhaseEulerFoam and to ensure correct operation
of models requiring formal boundedness of phase-fractions.

Resolves bug-report https://bugs.openfoam.org/view.php?id=2589

Henry Weller authored Jun 22, 2017 and Andrew Heather committed Jun 22, 2017

"pos" now returns 1 if the argument is greater than 0, otherwise it returns 0.
This is consistent with the common mathematical definition of the "pos" function:

https://en.wikipedia.org/wiki/Sign_(mathematics)

However the previous implementation in which 1 was also returned for a 0
argument is useful in many situations so the "pos0" has been added which returns
1 if the argument is greater or equal to 0.  Additionally the "neg0" has been
added which returns 1 if if the argument is less than or equal to 0.

Henry Weller authored Jul 13, 2017 and Andrew Heather committed Jul 13, 2017

Avoids potential problems with derived classes which do not define a clone function.

Original commit message:
------------------------

Parallel IO: New collated file format

When an OpenFOAM simulation runs in parallel, the data for decomposed fields and
mesh(es) has historically been stored in multiple files within separate
directories for each processor.  Processor directories are named 'processorN',
where N is the processor number.

This commit introduces an alternative "collated" file format where the data for
each decomposed field (and mesh) is collated into a single file, which is
written and read on the master processor.  The files are stored in a single
directory named 'processors'.

The new format produces significantly fewer files - one per field, instead of N
per field.  For large parallel cases, this avoids the restriction on the number
of open files imposed by the operating system limits.

The file writing can be threaded allowing the simulation to continue running
while the data is being written to file.  NFS (Network File System) is not
needed when using the the collated format and additionally, there is an option
to run without NFS with the original uncollated approach, known as
"masterUncollated".

The controls for the file handling are in the OptimisationSwitches of
etc/controlDict:

OptimisationSwitches
{
    ...

    //- Parallel IO file handler
    //  uncollated (default), collated or masterUncollated
    fileHandler uncollated;

    //- collated: thread buffer size for queued file writes.
    //  If set to 0 or not sufficient for the file size threading is not used.
    //  Default: 2e9
    maxThreadFileBufferSize 2e9;

    //- masterUncollated: non-blocking buffer size.
    //  If the file exceeds this buffer size scheduled transfer is used.
    //  Default: 2e9
    maxMasterFileBufferSize 2e9;
}

When using the collated file handling, memory is allocated for the data in the
thread.  maxThreadFileBufferSize sets the maximum size of memory in bytes that
is allocated.  If the data exceeds this size, the write does not use threading.

When using the masterUncollated file handling, non-blocking MPI communication
requires a sufficiently large memory buffer on the master node.
maxMasterFileBufferSize sets the maximum size in bytes of the buffer.  If the
data exceeds this size, the system uses scheduled communication.

The installation defaults for the fileHandler choice, maxThreadFileBufferSize
and maxMasterFileBufferSize (set in etc/controlDict) can be over-ridden within
the case controlDict file, like other parameters.  Additionally the fileHandler
can be set by:
- the "-fileHandler" command line argument;
- a FOAM_FILEHANDLER environment variable.

A foamFormatConvert utility allows users to convert files between the collated
and uncollated formats, e.g.
    mpirun -np 2 foamFormatConvert -parallel -fileHandler uncollated

An example case demonstrating the file handling methods is provided in:
$FOAM_TUTORIALS/IO/fileHandling

The work was undertaken by Mattijs Janssens, in collaboration with Henry Weller.

Will Bainbridge authored May 22, 2017 and Andrew Heather committed May 22, 2017

vectorField or vector2DField from scalarField components. To do this
properly and have it work for field-type combinations would require some
new field function macros.

- can be used to reduce copying