Dear OLB developers:
Here is how I set up the program using fresh download codes:
1. Go to ‘$openlbRoot/config.mk’, and switch “CXX:=mpic++”, “CXXFLAGS := $(OPTIM)”,”PARALLEL_MODE := MPI”, “BUILDTYPE := generic“。
2. Go to “$openlbRoot/examples/laminar/powerLaw2d/powerLaw2d.cpp”,
add macro “#define PARALLEL_MODE_MPI”. Within ‘void getResults()’ function, add the following lines to obtain the relaxation frequency: ” SuperLatticeField2D<T,DESCRIPTOR,olb::descriptors::OMEGA> omegaLB (sLattice);
vtmWriter.addFunctor( omegaLB );”
and ”
BlockReduction2D2D<T> planeReduction2( omegaLB, 600, BlockDataSyncMode::ReduceOnly );
heatmap::write(planeReduction, iT);”
3. Compile the source code using “make” command and execute the program using “mpirun -np 1 powerLaw2d”, “mpirun -np 2 powerLaw2d” and “mpirun -np 4 powerLaw2d”.
4. In these three cases with different numbers of MPI processes, the results of Omega field were
![Omega field using one MPI process](https://i.ibb.co/HVcztGF/MPI1-Ext-Fieldi-T0000160.jpg)
![Omega field using two MPI processes](https://i.ibb.co/3FnDW1p/MPI2-Ext-Fieldi-T0000160.jpg)
![Omega field using four MPI processes](https://i.ibb.co/MNZTnVR/MPI4-Ext-Fieldi-T0000160.jpg)
5. The problem is that, the Omega at cuboid block edges were discontinued, i.e., in the second map, there was a vertical line in the center, and in the third map, there were a vertical line and a horizontal line at the center.
I don’t know whether it is a problem within MPI post-processing or DynOmegaD2Q9Descriptor.
Thanks,
Junwei Guo