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Problem with MPI execution an LBM algorithm

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Viewing 7 posts - 1 through 7 (of 7 total)
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  • #1720
    Padde86
    Member

    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

    #2071
    jo
    Member

    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

    #2072
    Padde86
    Member

    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

    #2073
    jo
    Member

    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

    #2074
    Padde86
    Member

    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

    #2077
    mathias
    Keymaster

    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

    #2081
    Padde86
    Member

    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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