Difference between revisions of "Main Page/PIO"
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== Usage Introduction: == | == Usage Introduction: == | ||
| − | For | + | For ''traditional I/O'' approaches based on one file per processor, users can use #1,2,3 |
in .rea file for a specific example, by parameter 81. <br> | in .rea file for a specific example, by parameter 81. <br> | ||
These three approaches produce one file per processor and we will refer them as ''old libraries''. <br> | These three approaches produce one file per processor and we will refer them as ''old libraries''. <br> | ||
| Line 15: | Line 15: | ||
'''param(81) = 3''': use C-POSIX I/O libraries (binary, VTK format) ---> binary-xxx.vtk | '''param(81) = 3''': use C-POSIX I/O libraries (binary, VTK format) ---> binary-xxx.vtk | ||
| − | + | ||
Several ''advanced parallel I/O'' approaches were developed. Performance for those approaches | Several ''advanced parallel I/O'' approaches were developed. Performance for those approaches | ||
are detailed by Jing Fu et. al in Parallel I/O performance for application-level checkpointing | are detailed by Jing Fu et. al in Parallel I/O performance for application-level checkpointing | ||
Revision as of 11:10, 12 June 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:
For traditional I/O approaches based on one file per processor, users can use #1,2,3
in .rea file for a specific example, by parameter 81.
These three approaches produce one file per processor and we will refer them as old libraries.
param(81) = 1: use nek5000's http://nek5000.mcs.anl.gov/ old output format (ASCII) -> xxx.fld 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
Several advanced parallel I/O approaches were developed. Performance for those approaches
are detailed by Jing Fu et. al in Parallel I/O performance for application-level checkpointing
on the Blue Gene/P http://www.mcs.anl.gov/~mmin/ICS2011.pdf
param(81) = 4: collective IO for N proc IO 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(82) = number of output files param(83) = max number of fields to be written
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
