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:

For traditional 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 old_output format *.fld (ASCII).

param(81) = 2: use Fortran I/O library (ASCII, VTK format).

param(81) = 3: use C-POSIX I/O libraries (binary, VTK format).

---

Several advanced parallel I/O approaches were developed. The details are described[1]. #4, 5, 6, (-6), 8 indicate which I/O to use, as follows:

param(81) = 4: collective for N processors IO to 1 file (mpi-binary-N1.vtk)

param(81) = 5 is NM binary case: collective IO for N processors to multiple M-files.

param(103) = 6 is NM1 binary case: reduced-blocking IO for N processors to 1 file with M writers.

param(103) = 8 is NMM binary case (rbIO to M files with M writers).

param(103) = -6 is NM1 ASCII case (in tests it's refered to "7" instead of "-6").

Note that param(82) and param(83) need to be set correctly in *.rea file.

param(82) = number of groups, param(83) = max number of fields we are going to write.