Main Page/PIO
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