Changes between Version 14 and Version 15 of doc/app/machine/hlrnIII

Timestamp:

Feb 28, 2019 2:02:18 PM (6 years ago)

Author:

moh.hefny

Comment:

added MPI one-sided communication (RMA-MPI)

doc/app/machine/hlrnIII

@@ -17 +17 @@
 == Performance issues with runs using larger number of cores ==
 
+* '''FFT pressure solve'''
 Runs using the FFT pressure solver with core numbers > 10.000 may show substantially improved performance in case of setting the MPI environment variable {{{MPICH_GNI_MAX_EAGER_MSG_SIZE=16384}}} (the default value on the XC30 is 8192). It changes the threshold value for switching the data transfer with {{{MPI_ALLTOALL}}} from rendezvous to eager protocol.
 
@@ -22 +23 @@
 {{{
 %IC:[[ \$localhost = lccrayb ]]  &&  export MPICH_GNI_MAX_EAGER_MSG_SIZE=16384
+}}}
+
+* '''MPI one-sided communication (RMA-MPI)'''
+The raytracing algorithm in the radiation model uses MPI one-sided communication (MPI-RMA) to calculate the view factors (SVF) as well as the canopy sink factors (CSF). Performance degradation may occur when using large number of cores and the model halts during the calculation of SVF/CSF. In order to return performance, Special settings for some environmental variables have to be set.
+These setting can be realized by including, i.e., the following additional lines to the configuration file:
+{{{
+IC: export MPICH_RMA_OVER_DMAPP=1
+IC: export MPICH_RMA_USE_NETWORK_AMO=1
 }}}