- additional Pstream::broadcasts() method to serialize/deserialize
multiple items.
- revoke the broadcast specialisations for std::string and List(s) and
use a generic broadcasting template. In most cases, the previous
specialisations would have required two broadcasts:
(1) for the size
(2) for the contiguous content.
Now favour reduced communication over potential local (intermediate)
storage that would have only benefited a few select cases.
ENH: refine PstreamBuffers access methods
- replace 'bool hasRecvData(label)' with 'label recvDataCount(label)'
to recover the number of unconsumed receive bytes from specified
processor. Can use 'labelList recvDataCounts()' to recover the
number of unconsumed receive bytes from all processor.
- additional peekRecvData() method (for transcribing contiguous data)
ENH: globalIndex whichProcID - check for isLocal first
- reasonable to assume that local items are searched for more
frequently, so do preliminary check for isLocal before performing
a more costly binary search of globalIndex offsets
ENH: masterUncollatedFileOperation - bundled scatter of status
- the internal data are contiguous so can broadcast size and internals
directly without an intermediate stream.
ENH: split out broadcast time for profilingPstream information
STYLE: minor Pstream cleanup
- UPstream::commsType_ from protected to private, since it already has
inlined noexcept getters/setters that should be used.
- don't pass unused/unneed tag into low-level MPI reduction templates.
Document where tags are not needed
- had Pstream::broadcast instead of UPstream::broadcast in internals
- split off a Pstream::genericBroadcast() which uses UOPBstream during
serialization and UOPBstream during de-serialization.
This function will not normally be used directly by callers, but
provides a base layer for higher-level broadcast calls.
- low-level UPstream broadcast of string content.
Since std::string has length and contiguous content, it is possible
to handle directly by the following:
1. broadcast size
2. resize
3. broadcast content when size != 0
Although this is a similar amount of communication as the generic
streaming version (min 1, max 2 broadcasts) it is more efficient
by avoiding serialization/de-serialization overhead.
- handle broadcast of List content distinctly.
Allows an optimized path for contiguous data, similar to how
std::string is handled (broadcast size, resize container, broadcast
content when size != 0), but can revert to genericBroadcast (streamed)
for non-contiguous data.
- make various scatter variants simple aliases for broadcast, since
that is what they are doing behind the scenes anyhow:
* scatter()
* combineScatter()
* listCombineScatter()
* mapCombineScatter()
Except scatterList() which remains somewhat different.
Beyond the additional (size == nProcs) check, the only difference to
using broadcast(List<T>&) or a regular scatter(List<T>&) is that
processor-local data is skipped. So leave this variant as-is.
STYLE: rename/prefix implementation code with 'Pstream'
- better association with its purpose and provides a unique name
- The idea of broadcast streams is to replace multiple master to
subProcs communications with a single MPI_Bcast.
if (Pstream::master())
{
OPBstream toAll(Pstream::masterNo());
toAll << data;
}
else
{
IPBstream fromMaster(Pstream::masterNo());
fromMaster >> data;
}
// vs.
if (Pstream::master())
{
for (const int proci : Pstream::subProcs())
{
OPstream os(Pstream::commsTypes::scheduled, proci);
os << data;
}
}
else
{
IPstream is(Pstream::commsTypes::scheduled, Pstream::masterNo());
is >> data;
}
Can simply use UPstream::broadcast() directly for contiguous data
with known lengths.
Based on ideas from T.Aoyagi(RIST), A.Azami(RIST)
