Axisymmetry is necessary to ensure that the problem is of manageable size. Worldwide, little work has been done on the general problem because of the computing time needed. However, as progress is made towards a teraflop machine there is likely to be a substantial growth of interest in relativity codes, which is why the code was chosen as part of the benchmark suite. The algorithm is parallel in y. The host process creates the node processes, each at a different value of y, sends initial information and collects the results.
Message passing is mainly between nearest neighbours, in calculating y-derivatives.
However, messages are also passed to and from the host at every step in the evolution to smooth the data at the I1 r-points nearest to the origin. The code uses double precision throughout. The grid is partitioned in the y-direction on a grid of PN processors. After NI time-steps, an estimate of the error is output, and after NR such reports the program terminates. The problem size is specified by parameter statements in the file gr1.