551.ppalm
SPEC ACCEL Benchmark Description File

Benchmark Name

551.ppalm

Benchmark Author

Siegfried Raasch, Leibniz University of Hannover

Initial port to OpenMP by Alexander Grund

Benchmark Program General Category

Large-eddy simulation, atmospheric turbulence

Benchmark Description

PALM is a large-eddy simulation (LES) model for atmospheric and oceanic flows which is especially designed for performing on massively parallel computer architectures. PALM is free software. It can be redistributed and/or modified under the terms of the GNU General Public License (v3).

PALM solves prognostic equations for velocity (Navier-Stokes equation), temperature (first law of thermodynamics) and humidity (transport equation for scalar). A Boussinesq approximation for incompressible fluids is used. Equations are discretized on a cartesian staggered grid using finite differences.

Some of PALM's highlights are:

• excellent scaling, so far tested up to 32000 cores
• online data analysis (during model runs) in order to avoid I/O bottlenecks
• topography realized on cartesian grid (allows for steep topography)
• non-cyclic horizontal boundary conditions including turbulent inflow
• code can be switched to ocean version with salinity equation and equation of state for seawater
• embedded parallelized Lagrangian particle model for various applications (footprint calculation, simulation of cloud droplet growth, visualization, etc.)
• interface which allows users to plug in their own code extensions without modifying the default code
• advanced shell scripts for installing and running the code in interactive and batch mode are available
• code is permanently maintained and improved by the PALM group and other users; code management is based on subversion

Input Description

The input parameter file describes a model setup for idealized atmospheric convection. The atmosphere is initially at rest and heated from the surface with a constant rate of about 100 Watt per square meter.

Output Description

The output file serves as a standard check for the reliabilty of the simulation results. One line is output per model timestep. Beside the simulated time, it mainly displays the temporal evolution of the absolute maximum of the three velocity components (umax, vmax, wmax) in meter per second.

Programming Language

Fortran

Known portability issues

None.

Reference

PALM Homepage

Raasch, S. and M. Schröter, 2001: PALM - A large-eddy simulation model performing on massively parallel computers. Meteorol. Z., 10, 363-372. DOI: 10.1127/0941-2948/2001/0010-0363. pdf