Virtual memory utilization in large plasma simulation codes

Large two and three dimensional plasma simulation codes require the use of large slow storage devices such as magnetic discs as extensions to fast store. Both particle (or fluid) quantities and field quantities must reside on disc, making random access to the entire field arrays impossible. A method of bookkeeping which requires only a subset of the field arrays to be in core at one time and which minimizes lost computer time due to I/O wait is described. Particles are treated in groups, each of which resides in a local region of the plasma, necessitating the simultaneous presence in core of only those field quantities overlapping that region. A method of implementing field solvers which use fast Fourier transforms is given which is useful when the field arrays are too large to fit in core. (U.S.)