- UPstream::globalComm constant always refers to MPI_COMM_WORLD but
UPstream::worldComm could be MPI_COMM_WORLD (single world)
or a dedicated local communicator (for multi-world).
- provide a Pstream wrapped version of MPI_COMM_SELF,
references as UPstream::selfComm
- UPstream::isUserComm(label)
test for additional user-defined communicators
- 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
- Pstreams can be ascii/binary but are always currentVersion
- rename UIPstream externalBuf_ to 'recvBuf_' for similar naming as
PstreamBuffers and symmetry with UOPstream::sendBuf_
- specific enum size for commsType (for more compact structures in the
future). Default construct lists items.
BUG: possible incidental indexing in UIPstream::read(char*, std::streamsize)
- raw reading had been split into beginRawRead(), readRaw().
However, this could change the current input position (due to word
boundary alignment), even if the expected count is zero. Make a
no-op for count == 0. This mirrors UOPstream::write behaviour.
