Gabriele Cosmo
61 lines
2.1 KiB
Markdown
61 lines
2.1 KiB
Markdown
\page ExampleexMPI04 Example : exMPI04
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MPI/Examples : exMPI04
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======================
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Description
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-----------
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An example of dosimetry in a water phantom.
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The example is as exMPI03, but adds output in G4analysis ntuple
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and demonstrates ntuple merging.
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In difference from merging other data (G4Run, scorers, hitograms),
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the ntuple data are not sent to the collecting rank(s) at the
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end of run but during event processing. That's why (an) extra rank(s)
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have to be reserved for this purpose. The number of extra workers requested
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is set in G4MPImanager constructor in main(). While G4MPImanager
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can be created with any number of extra workers (< total number),
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the ntuple merging is at present supported only for one.
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The extra worker is connected to the run action class via G4MPIextraWorker
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object which is set to G4MPImanager in main().
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The standard calls to G4AnalysisManager (creating ntuple, open, write and
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close file) trigger creating all necessary analysis tools object
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for merging ntuple data on flight.
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MPI ntuple merging can be activated in sequential mode only;
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this activation is perfomed by creating the G4MPIntupleMerger
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object in the RunActionMaster constructor.
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The merger must be created before creating G4AnalysisManager
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(= the first call to G4AnalysisManager::Instance())
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and deleted only at the end of program.
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If multithreading mode is enabled, the ntuples are merged from
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threads to files per ranks.
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Combined MT + MPI merging is not yet supported.
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Merging ntuples is actually supported only with Root output format.
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How to build
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------------
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Use CMake on Geant4 library installed with CMake build.
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This example requires G4mpi library to be installed
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(see examples/extended/parallel/MPI/source/REDME.md)
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Follow these commands,
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> mkdir build
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> cd build
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> cmake -DG4mpi_DIR=<where-G4mpi-wasintalled>/lib[64]/G4mpi -DCMAKE_CXX_COMPILER=mpicxx \
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-DGeant4_DIR=<your Geant4 install path>/lib[64]/Geant4-V.m.n <path-to-source>
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(V.m.n is the version of Geant4, eg. Geant4-9.6.0)
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> make
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> make install
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Replace mpicxx with your MPI-compiler wrapper.
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How to run
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----------
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> mpiexec -n # ./exMPI04 [run.mac]
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