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Manuscript Title: Dynamic information retrieval of atomic codes II. Implementation.
Authors: A.R. Davies, K. Smith, K.L. Kwok
Program title: DIRAC
Catalogue identifier: AAIB_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 6(1973)165
Programming language: Fortran.
Computer: IBM 360/65.
Operating system: OS/360-MVT.
Program overlaid: yes
RAM: 200K words
Word size: 8
Peripherals: disc.
Keywords: Cross sections, Electron scattering, Graphical display, Information retrieval, Interactive, Photoionization, Database.
Classification: 9.

Subprograms used:
Cat Id Title Reference
AAIC_v1_0 DATBNK CPC 6(1973)165

Nature of problem:
DIRAC (dynamic information retrieval of atomic codes) is a program which dynamically retrieves information from a databank upon a users request and displays this information on an online graphical display unit. The display can be tabular or graphical of any of the data stored in the databank. The databank is itself formed by DIRAC and is automatically updated if runs are initiated by the user from the display unit. The system can be used by any collection of theoretical codes for calculating cross sections; experimental points can also be fed into the databank.

Solution method:
A user sits in front of the graphics display unit with an alphanumeric keyboard and with the use of a light pen and programmed function key- board buttons is taken through a selection procedure by interacting with the display frames appearing on the unit. The atomic collision physics problem of interest to the user is built up by selecting the appropriate constants of the problem. Finally the answers to the problem can be displayed graphically or tabularly if they exist or if they do not exist, new runs can be instigated using codes like SEBAS and ATOMNP to produce the new data. A complete description of the user options is given in a first paper.

Restrictions:
Data is in the form of discrete points which can be plotted on a rectangular set of axes where the absissa is always taken to be energy (except for differential cross sections which is in radians) and the ordinate is the physical data. The fundamental restrictions are defined in the design characteristics of the directories. In general terms, these are determined by the rules of L-S coupling in collision processes.

Unusual features:
The entire memory heirarchy (core, disc, data cell and magnetic tape) is used dynamically by Dirac to optimize its use of the computer resources. A routine is incorporated into DIRAC by which the user can initiate runs of the computer codes, which updates the data bank, directly from the "physics frames". To run this program on other manufacturer's equipment will require the user to supply equivalent routines to those taken from the IBM graphic subroutine package.

Running time:
As the program is run in an interactive mode with the user in front of the graphics device then the analysis of existing data takes place in real time. Retrieving the complete physics data for several hundred points takes of the order of 10 s. Plotting these points and drawing the curves on the screen takes of the order of 10 s. The computation and plotting of reasonance shapes is immediate.