Difference between revisions of "Main Page/PIO"
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Jump to navigationJump to search| Line 7: | Line 7: | ||
== Usage Introduction == | == Usage Introduction == | ||
| − | + | Users can use #1,2,3,4,5,6,7,8 in .rea file for a specific example, by parameter 81. <br> | |
| − | in .rea file for a specific example, by parameter 81. <br> | ||
'''param(81) = 1''': use nek5000's [http://nek5000.mcs.anl.gov/] old output format (ASCII) -> xxx.fld | '''param(81) = 1''': use nek5000's [http://nek5000.mcs.anl.gov/] old output format (ASCII) -> xxx.fld | ||
| − | + | 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) = 2''': use Fortran I/O library (ASCII, VTK format) ---> ascii-xxx.vtk | ||
| Line 18: | Line 17: | ||
| − | Several '''advanced parallel I/O''' approaches were developed. Performance for those approaches | + | Several '''advanced parallel I/O''' approaches based on MPI-IO library were developed. |
| − | are detailed in<br> | + | Performance for those approaches are detailed in<br> |
''Jing Fu et. al, Parallel I/O performance for application-level checkpointing on the Blue Gene/P '' [http://www.mcs.anl.gov/~mmin/ICS2011.pdf] | ''Jing Fu et. al, Parallel I/O performance for application-level checkpointing on the Blue Gene/P '' [http://www.mcs.anl.gov/~mmin/ICS2011.pdf] | ||
Revision as of 12:21, 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
Users can use #1,2,3,4,5,6,7,8 in .rea file for a specific example, by parameter 81.
param(81) = 1: use nek5000's [1] old output format (ASCII) -> xxx.fld
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
Several advanced parallel I/O approaches based on MPI-IO library were developed.
Performance for those approaches are detailed in
Jing Fu et. al, Parallel I/O performance for application-level checkpointing on the Blue Gene/P [2]
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(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
