Multisend available in NEURON by default.

[nrnhines]

Turn off default printing of multisend setup space/performance info.
This is also done in BlueBrain/CoreNeuron#692

pc.spike_compress(-1) acts according to documentation (does not
change any multisend properties).

neuron.coreneuron specifies correct multisend args derived
from current NEURON settings from pc.spike_compress third arg
(available from pc.send_time(8))

test using https://github.com/nrnhines/tqperf

git checkout hines/test1
nrnivmodl -coreneuron mod
mpiexec -n 4 nrniv -mpi -python test1.py

[codecov-commenter]

Codecov Report

Merging #1537 (a3c49cc) into master (903136d) will decrease coverage by 0.18%.
The diff coverage is 63.63%.

@@            Coverage Diff             @@
##           master    #1537      +/-   ##
==========================================
- Coverage   43.97%   43.79%   -0.19%     
==========================================
  Files         550      552       +2     
  Lines      110410   110973     +563     
==========================================
+ Hits        48558    48602      +44     
- Misses      61852    62371     +519     

Impacted Files	Coverage Δ
share/lib/python/neuron/coreneuron.py	76.92% <0.00%> (ø)
src/nrniv/bgpdmasetup.cpp	0.00% <ø> (ø)
src/nrnoc/nrntimeout.cpp	53.84% <ø> (ø)
src/nrniv/netpar.cpp	81.24% <100.00%> (-0.36%)	⬇️
src/nrnoc/hocprax.cpp	65.38% <100.00%> (ø)
src/nrniv/structpool.h	77.58% <0.00%> (-10.65%)	⬇️
src/nrnmpi/mpispike.cpp	61.99% <0.00%> (-4.12%)	⬇️
src/nrniv/bbsavestate.cpp	89.80% <0.00%> (-0.06%)	⬇️
src/nrniv/bgpdma.cpp	8.30% <0.00%> (ø)
... and 2 more

---

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[nrnhines]

@pramodk Note that when building with -DNRN_ENABLE_MPI_DYNAMIC="ON" Then ninja test generates

         33 - external_ringtest::coreneuron_cpu_mpi_offline (Failed)
         36 - external_ringtest::compare_results (Failed)
         40 - testcorenrn_bbcore::coreneuron_cpu_offline (Failed)
         42 - testcorenrn_bbcore::compare_results (Failed)
         46 - testcorenrn_deriv::coreneuron_cpu_offline (Failed)
         48 - testcorenrn_deriv::compare_results (Failed)
         52 - testcorenrn_gf::coreneuron_cpu_offline (Failed)
         54 - testcorenrn_gf::compare_results (Failed)
         56 - testcorenrn_patstim::coreneuron_cpu_offline (Failed)
         58 - testcorenrn_patstim::compare_results (Failed)
         62 - testcorenrn_vecplay::coreneuron_cpu_offline (Failed)
         64 - testcorenrn_vecplay::compare_results (Failed)
         68 - testcorenrn_vecevent::coreneuron_cpu_offline (Failed)
         70 - testcorenrn_vecevent::compare_results (Failed)
         74 - testcorenrn_watch::coreneuron_cpu_offline (Failed)
         76 - testcorenrn_watch::compare_results (Failed)
         80 - testcorenrn_conc::coreneuron_cpu_offline (Failed)
         82 - testcorenrn_conc::compare_results (Failed)
         86 - testcorenrn_kin::coreneuron_cpu_offline (Failed)
         88 - testcorenrn_kin::compare_results (Failed)

Due to For dynamic MPI support you must pass '--mpi-lib ...' explicitly needed in offline mode. I'm wondering if it would be more convenient to look for that info in a NRNCORE_NRNMPILIB environment variable set by user if --mpi-lib is not present.
Otherwise, some CMakeLists.txt files would need to augment MPIEXEC_POSTFLAGS for the special-core tests, and that might be difficult to choose. Alternatively the code that loads libmpi... could figure out what libnrnmpi... to load just like is done on the NEURON side.

[nrnhines]

I don't see how --mpi-lib /path/... can work in offline mode since ldd libcorenrnmpi_ompi.so does not list libmpi... and coreneuron does not explicitly dlopen the latter. (On the NEURON side, libmpi is dlopen first and, if successful, then the compatible libnrnmpi is dlopen.)