ENH: eliminate unnecessary duplicate communicator
- in globalMeshData previously had a comm_dup hack to avoid clashes
with deltaCoeffs calculations. However, this was largely due to a
manual implementation of reduce() that used point-to-point
communication. This has since been updated to use an MPI_Allreduce
and now an MPI_Allgather, neither of which need this hack.
- bundles frequently used 'gather/scatter' patterns more consistently.
- combineAllGather -> combineGather + broadcast
- listCombineAllGather -> listCombineGather + broadcast
- mapCombineAllGather -> mapCombineGather + broadcast
- allGatherList -> gatherList + scatterList
- reduce -> gather + broadcast (ie, allreduce)
- The allGatherList currently wraps gatherList/scatterList, but may be
replaced with a different algorithm in the future.
STYLE: PstreamCombineReduceOps.H is mostly unneeded now
- Favour use of argList methods that are more similar to dictionary
method names with the aim of reducing the cognitive load.
* Silently deprecate two-parameter get() method in favour of the
more familiar getOrDefault.
* Silently deprecate opt() method in favour of get()
These may be verbosely deprecated in future versions.
- With argList::noFunctionObjects() we use the logic added in
4b93333292 (issue #352)
By removing the '-noFunctionObjects' option, we automatically
suppress the creation of function-objects via Time (with argList
as a parameter).
There is generally no need in these cases for an additional
runTime.functionObjects().off() statement
Use the argList::noFunctionObjects() for more direct configuration
and reduce unnecessary clutter in the -help information.
In previous versions, the -noFunctionObjects would have been redundant
anyhow, so we can also just ignore it now instead.
General:
* -roots, -hostRoots, -fileHandler
Specific:
* -to <coordinateSystem> -from <coordinateSystem>
- Display -help-compat when compatibility or ignored options are available
STYLE: capitalization of options text
- relocate some standard functionality to TimePaths to allow a lighter
means of managing time directories without using the entire Time
mechanism.
- optional enableLibs for Time construction (default is on)
and a corresponding argList::noLibs() and "-no-libs" option
STYLE:
- mark Time::outputTime() as deprecated MAY-2016
- use pre-increment for runTime, although there is no difference in
behaviour or performance.
- Since 'bool' and 'Switch' use the _identical_ input mechanism
(ie, both accept true/false, on/off, yes/no, none, 1/0), the main
reason to prefer one or the other is the output.
The output for Switch is as text (eg, "true"), whereas for bool
it is label (0 or 1). If the output is required for a dictionary,
Switch may be appropriate. If the output is not required, or is only
used for Pstream exchange, bool can be more appropriate.
- 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();
...
}
- use succincter method names that more closely resemble dictionary
and HashTable method names. This improves method name consistency
between classes and also requires less typing effort:
args.found(optName) vs. args.optionFound(optName)
args.readIfPresent(..) vs. args.optionReadIfPresent(..)
...
args.opt<scalar>(optName) vs. args.optionRead<scalar>(optName)
args.read<scalar>(index) vs. args.argRead<scalar>(index)
- the older method names forms have been retained for code compatibility,
but are now deprecated
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.
