- 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)
