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Manuscript Title: P3M3DP: the three dimensional periodic particle-particle/particle- mesh program.
Authors: J.W. Eastwood, R.W. Hockney, D.N. Lawrence
Program title: P3M3DP
Catalogue identifier: ABVA_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 19(1980)215
Programming language: Fortran.
Computer: IBM 360/195.
Operating system: OS-MVT.
RAM: 248K words
Word size: 8
Keywords: Many body force Calculation, Three dimensional, Particle-particle/ Particle-mesh (p3m), Ionic liquids, Three dimension vlasov Gas, Particle-mesh plasma Simulation, Many body gravitating System, Plasma physics, Pppm, Collisionless plasma.
Classification: 19.3.

Subprograms used:
Cat Id Title Reference
ABUF_v1_0 OLYMPUS CPC 7(1974)245
ABUF_v2_0 OLYMPUS FOR IBM 370/165 CPC 9(1975)51
ABUF_v3_0 OLYMPUS FOR CDC 6500 CPC 10(1975)167
ABUA_v1_0 FOUR67 CPC 2(1971)127

Nature of problem:
The program can be used to simulate many body classical systems where interparticle forces are central and conservative. It is particularly effective for systems with rapidly varying short range forces plus long range Coulombic forces as is found in the simulation of ionic liquids or in the clustering of galaxies, although other systems, such as Lennard-Jones liquids and Vlasov plasmas can also be handled.

Solution method:
Interparticle forces are decomposed into spatially localised parts and approximately band limited parts. Accelerations are computed by using a direct particle-particle (PP) summation over the spatially localised forces and a particle-mesh (PM) method for the band limited forces. The equations of motion are approximated by the leapfrog scheme. The resulting PPPM (orP**3M) algorithm has the advantages that spatial resolution is not limited by mesh size as in PM schemes and cycle time is proportional to the number, Np, of particles rather than N**2 p as in a purely PP method with long-range forces.

The implementation of the PPPM algorithm in this program is restricted to a triply periodic cubical computational box and a long-range force which is purely Coulombic.

Unusual features:
The program is written in standard FORTRAN using the OLYMPUS conventions for structure, layout, notation and documentation. Graphical interface routines (the RDIPLT package) are included in documented dummy form so that potential users can include their own versions of obtain RDIPLT when it is published.

Running time:
The cpu time, T (in seconds), on an IBM 360/195 for a single timestep is approximately (to within ~~10%) given by T = (50+2Nn) 10**-5Np+Beta(Ng) where Nn = number of particles in a sphere whose radius equals the range, re, of the short range force, Np is the number of particles and Beta (Ng) is the time for solving the mesh equations (Beta ~~ 0.3 for Ng = 16, 2.0 for Ng = 32 and 12 for Ng = 64). Typically, the program takes 1.5 s/1000 particles/timestep. T includes the time for the dynamical calculation and the time for calculation of pressure, temperature, internal energy and radial distribution function.