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A potential difficulty with mixed model equations for multiple trait evaluation of sires is solving the equations as the number of equations increases proportionally to the number of traits. Time required to obtain inverse solutions increases by the number cubed. Thus, iterative procedures often are used. Three iterative procedures, successive overrelaxation, block iteration with relaxation, and the method of conjugate gradients, were compared for four sets of multiple trait equations for sire evaluation. Equations were solved after absorption of equations for random herd-year-season effects. Equations for two and four traits each with test and complete data sets made up the four sets of equations. The two-trait system featured high heritabilities and large negative correlations among effects whereas the four-trait system had low heritabilities and smaller negative correlations. Rate of convergence for block iteration was faster than for successive overrelaxation, especially for the four-trait system and especially for more exacting convergence criteria. The method of conjugate gradients was efficient only for test data sets (30 and 60 equations) and was not competitive with the other methods for complete data sets (1426 and 2852 equations). Test data sets accurately predicted optimum relaxation factors for successive overrelaxation for complete data sets. Optimum relaxation factor for the two-trait system was 1.5 to 1.7 and for the four-trait system was 1.3 to 1.5. Gauss-Seidel iteration took 33 to 400%Received April 30, 1984. more rounds than successive overrelaxation with the optimum relaxation factor depending on stopping criteria and data set.

Gauss-Seidel, successive overrelaxation, end-of-round relaxation, and block iteration methods of obtaining solutions for sire effects from equations rising from progeny with records in mixed model procedures were compared. Equations transformed to provide direct solutions for genetic group plus sire effects as well as constrained and unconstrained equations were compared also. Equations for milk yield for the Northeast Artificial Insemination Sire Comparison numbered 301 for Ayrshires, 325 for Brown Swiss, 6,010 for Holsteins, and 926 for Jerseys after absorption of herd-year-season effects. Numbers of coefficients were 15 to 20% less for transformed equations, which decreased computing time per round of interation about 15%. Solutions for transformed equations converged more rapidly than solutions for untransformed equations with convergence criterion the ratio of the residual norm to the norm of the right-hand sides. Successive overrelaxation generally was more efficient than Gauss-Seidel iteraton. Solutions for equations constrained to full rank converged more slowly than unconstrained equations. Block iteration was more efficient than single equation iteration.

The national laboratories and NSF supercomputer centers have been discussing online information systems since 1990. Initially these discussions considered appropriate standards for vendor and locally written documents. An integrated system across the centers was not originally envisioned. With the initiation of the Metacenter and the development and acceptance of distributed client/serverbased tools such as WAIS, gopher, and World Wide Web, the time was right for a single repository for online information about high-performance computing and communications. AbstractBelow is a timeline for the evolution of the Metacenter Online Information System from concept to preliminary completion: