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Manuscript Title: The parallel computation of Racah coefficients using transputers.
Authors: N.S. Scott, P. Milligan, H.W.C. Riley
Program title: PRACAH
Catalogue identifier: AAXE_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 46(1987)83
Programming language: OCCAM.
Computer: IMS B002 TRANSPUTER.
Operating system: IMS B002 TRANSPUTER DEVELOPMENT SYSTEM.
RAM: 1000K words
Word size: 32
Keywords: General purpose, Rotation group, Software, Occam, Transputer, Concurrency, Parallel processing, Racah coefficient, Scattering, Structure, Computers.
Classification: 4.1, 6.5.

Nature of problem:
This paper is concerned with the calculation of Racah coefficients. These coefficients are required in the construction of angular integrals in atomic structure and scattering calculations.

Solution method:
A number of Racah coefficient programs have been published in CPC. This program is different in that it is a parallel solution programmed in OCCAM and executed on a network of TRANSPUTERS.

Restrictions:
For simplicity, the program driver designed for the test-run requires the Racah coefficient arguments to have values less than or equal to 4.5.

Unusual features:
The FOLDING EDITOR used by the TRANSPUTER Development System makes use of special control codes. Because of the need to distribute the program as card images the program is published in the form of a printable listing. The user can easily insert appropriate folds using the FOLDING EDITOR. It should be noted that the three processes, master, sum and delta need to be treated as semi-compiled folds. The two processes FLOAT32 and B002.terminal.driver which are provided in the IMS D600 TRANSPUTER Development System are not published because of copyright reasons. These should be inserted into the program at the points indicated by ...FLOAT32 and ..B002.terminal.driver respectively.

Running time:
Timing details are given in section 3.3. The complete test-run timed on the B002 Board took 2879376 cycles (2.88 secs) for 600 Racah coefficients.