Difference between revisions of "Main Page/PIO"
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Users can use #1,2,3,4,5,6,7,8 in .rea file for a specific example, by parameter 81. <br> | Users can use #1,2,3,4,5,6,7,8 in .rea file for a specific example, by parameter 81. <br> | ||
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Several '''advanced parallel I/O''' algorithms based on MPI-IO library were developed. <br> | Several '''advanced parallel I/O''' algorithms based on MPI-IO library were developed. <br> | ||
| − | + | The analysis on the performance for those approaches are detailed in ''Parallel I/O | |
| − | approaches are detailed in ''Parallel I/O performance for application-level checkpointing | + | performance for application-level checkpointing on the Blue Gene/P, by Jing Fu et. al.'' [http://www.mcs.anl.gov/~mmin] |
| − | on the Blue Gene/P, by Jing Fu et. al.'' [http://www.mcs.anl.gov/~mmin | ||
proc=processors | proc=processors | ||
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'''Note''' that param(82) and param(83) need to be set correctly in *.rea file. | '''Note''' that param(82) and param(83) need to be set correctly in *.rea file. | ||
| + | '''param(80)''' = ''exact'' total number of fields to be written | ||
| + | '''param(82)''' = number of output files | ||
| + | '''param(83)''' = frequency of restart output files, 0 (no restart output), #nn (iostep*nn) | ||
| + | '''param(84)''' = invoked with dump_number from the name of the restarting output file | ||
| − | |||
| − | |||
---- | ---- | ||
Latest revision as of 22:36, 16 December 2011
This is the document page for parallel I/O library developed for NekCEM.
Background
- File Format
- Binary (used for production, compact size), or ASCII (used for debugging, human-readable)
Usage Introduction
Users can use #1,2,3,4,5,6,7,8 in .rea file for a specific example, by parameter 81.
Several advanced parallel I/O algorithms based on MPI-IO library were developed.
The analysis on the performance for those approaches are detailed in Parallel I/O
performance for application-level checkpointing on the Blue Gene/P, by Jing Fu et. al. [1]
proc=processors param(81) = 4: collective IO for N proc to 1 file ---> mpi-binary-N1-xxx.vtk param(81) = 5: collective IO for N proc to multiple M-files ---> mpi-binary-NM-xxx.vtk param(81) = 6: reduced-blocking IO for N proc to 1 file with M writers ---> mpi-binary-NM1-xxx.vtk param(81) = 7: reduced-blocking IO for N proc to 1 file with M writers ---> mpi-ascii-NM1-xxx.vtk param(81) = 8: reduced-blocking IO for N proc to multiple M-files with M writers ---> mpi-binary-NMM-xxx.vtk
Note that param(82) and param(83) need to be set correctly in *.rea file.
param(80) = exact total number of fields to be written param(82) = number of output files param(83) = frequency of restart output files, 0 (no restart output), #nn (iostep*nn) param(84) = invoked with dump_number from the name of the restarting output file
For traditional I/O approaches based on one file per processor, using old libraries, one can use
param(81) = 2: use Fortran I/O library (ASCII, VTK format) ---> ascii-xxx.vtk param(81) = 3: use C-POSIX I/O libraries (binary, VTK format) ---> binary-xxx.vtk
param(81) = 1: use nek5000's old output format (ASCII) -> xxx.fld
Visualization
The output files with param(81)=2,3,4,5,6,7,8 can be visualized with ParaView and VisIt.
The output with param(81)=1 can be visualized with nek5000 visualization tool, postx
