Reading and writing IEEE and Cray binary data on Cray systems

This article discusses how to read or write files that are in IEEE binary or Cray binary format. It is intended for users of the Cray PVP (parallel vector processor) computers and the Cray T3D.

The basic technique is to use the ASSIGN statement to specify the format (Cray binary or IEEE binary), the word size (4-byte or 8-byte), and the blocking and control words.

The relevant syntax of the assign statement is:

    assign -N [see Table 1] -F [see Table 2] u:unit

where the values of -N and -F are given in the following two tables.

    Table 1. 'assign -N' determines format and word size

    +----------++--------------------+-------------------+
    |  -N      || Read/Write on CRAY | Read/Write on T3D |
    +----------++--------------------+-------------------+
    +----------++--------------------+-------------------+
    | [none]   ||  Cray  R*8/I*8     |  IEEE  R*8/I*8    |
    +----------++--------------------+-------------------+
    | cray     ||  Cray  R*8/I*8     |  Cray  R*8/I*8    |
    +----------++--------------------+-------------------+
    | ieee_64  ||  IEEE  R*8/I*8     |      n/a          |
    +----------++--------------------+-------------------+
    | ieee_dp  ||  IEEE  R*8/I*4     |      n/a          |
    +----------++--------------------+-------------------+
    | [note 1] ||  IEEE  R*4/I*8     |      n/a          |
    +----------++--------------------+-------------------+
    | ieee     ||  IEEE  R*4/I*4     |      n/a          |
    | ieee_32  ||                    |                   |
    +----------++--------------------+-------------------+



    Table 2. 'assign -F' determines blocking and control words

    +----------++-------------------------------+
    |  -F      || Read/Write on Cray or T3D     |
    +----------++-------------------------------+
    +----------++-------------------------------+
    | [none]   || COS-blocking                  |
    +----------++-------------------------------+
    | cos      || COS-blocking                  |
    +----------++-------------------------------+
    | f77      || F77 control words (I*4 at     |
    |          || start and end of each record) |
    +----------++-------------------------------+
    | null     || No blocking, no control words |
    +----------++-------------------------------+

    Note 1:
    Currently available only on shavano and echo. Compile with:
       cf77 -Wl"-F" ~kuehn/IEEE_conversion/fp32_int64.o  your.prog.f
    and use:
       assign -N user u:10    # Add -F as desired/necessary

Example 1

To read/write an IEEE file with 8-byte reals, 4-byte integers, and Fortran control words, on a Cray, on Fortran unit 10, use this assign statement:

    assign -N ieee_dp -F f77 u:10

Example 2

To read/write a Cray binary file, with 8-byte reals, 8-byte integers, and COS-blocked binary data on the T3D, use this assign statement:

    assign -N cray -F cos u:10