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:

Generally, several new parallel I/O approaches were developed, namely #3, 4, 5, 6, 7, 8. These numbers were used to indicate which I/O to use, in .rea file for a specific example, by parameter 81.

param(81) = 1 means it's using nek5000 output format *.fld (ASCII).
param(81) = 2 mean it's using Fortran I/O library to write ASCII files in VTK format.
param(81) = 3 means it's using C-POSIX I/O libraries to write binary files.
These three approaches produce one file per processor and we will refer them as old libraries.

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param(81) = 4 is N1 binary case: collective IO to 1 file.

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.