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 103.

param(103) = 1 and param(103) = 2 mean it's using Fortran I/O library to write binary and ASCII files. These two approaches would produce one file per processor and we will refer them as old libraries.
param(103) = 3 means it's using C-POSIX I/O libraries to write binary files.

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param(103) = 4 is N1 binary case (syncIO to 1 file).

param(103) = 5 is NM binary case (syncIO to M files).

param(103) = 6 is NM1 binary case (rbIO 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.

Implementation Details:

Topology of code

• I/O functions were initiated from cem_out function of cem_dg.F (and cem_dg2.F).
• Implementation of parallel I/O routine were defined in vtkbin.c and rbIO_nekcem.c
• vtkcommon.c and vtkcommon.h serve as a place to hold common functions as well as global variables.
  

• .box &rarr num elements in x,y,z
• .rea &rarr input data
• SIZEu
  • lp = #proc
  • lelx = 20 each dimension
  • lelv = alloc max # of element per proc

To-do List

• More parameter with ng = M and 1< nf < M
• Tests on Kraken and Jaguar

Some notes

• Fortran generated binary file may not be correctly read in C.