Problem with MPI execution an LBM algorithm

[Padde86]

Hello everybody,rnrnI am using now OpenLB and I am complete new to C++ and the LBM so I got two questions:rnrn1. when i try to perfom a parallel execution with mpiexec -np 4 ./cylinder3d , the same programm is four times running serial on four different nodes wich is very unnecessary. How do i fix that? rnrn2. The same example cylinder3d: after serial execution the main file says i have 252nx nodes and 43 nodes for the y- and z- direction. Where do these values come from? when i look in “”blockGeometry.cpp”” i find a “”setNx()”” and “”getNx()”” but when i set Nx/Ny/Nz in the main programm I only move the domain and do not refine the solution. for a higher solution of 252x43x43 I get an error “”segmentation fault””rnrnI would be very thankfull for any help.rnrnbest rnpatrick

[jo]

Hi Patrick,rnrn1. Did you change the compiler flags in “”Makefile.inc””? There should be PARALLEL_MODE := MPI and the compiler changed to your parallel one.rn2. They come from the voxilization in “”stlreader.read(blockGeometry, 0u, 250);””. Here, 250 indicated the resolution in 0u, i.e. x-direction.rnrnJo

[Padde86]

Hey Jo,rnrn1. Yeah I changed this flag before but still multiple execution and seriel compuatitonrn2. Oh man that is awkward… I overlooked this the whole time.rnrnThanks a lot rnPatrick

[jo]

Dear Patrick,rnrn1. Did you recompile the code by 1. “”make cleanbuild””, 2. “”make clean”” and 3. “”make””? Can you use mpirun instead mpiexec? Did you measure the execution times?rnrnJo

[Padde86]

Hallo Jo,rnrnyes I performed those three steps but still no correct execution. When I clean the build and subsequent compile the code new I am not even able to compile the cylinder3D.cpp since multiple MPI_Request errors appear.rnrnthanks for your helprnrnbest rnpatrick

[mathias]

Dear Patrick,rnrn Please download release 1 of 0.7 if you have not done yet. Further, please send the Makefile.inc you are using to bug@openlb.net . I am using gcc 4.4.3 and openmpi and just tested this example which was working fine.rnrnMathias

[Padde86]

Problem solved:rnrnthe compiler for mpi execution had to be changed. Instead ofrnrnCXX = mpiCCrnit shopuld be changed tornCXX = mpic++rnrnthanks to everybody for the helprnrnbest patrick

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