One alternative that I like and it integrates well with mpi is the global arrays toolkit http://www.emsl.pnl.gov/docs/global/ -- Jaime D. Perea Duarte. <jaime at iaa dot es> Linux registered user #10472 Dep. Astrofisica Extragalactica. Instituto de Astrofisica de Andalucia (CSIC) Apdo. 3004, 18080 Granada, Spain.