Difference between revisions of "PALM"

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[[FILE:palm_scaling_c_flow.png|170px|center]]
[[FILE:palm_scaling_c_flow.png|170px|center]]


This is a first guess from a sample of simulation data. However, this number might have to be corrected in the future.
This value is a first guess from a sample of simulation data. However, this number might have to be corrected in the future. It depends on additional parameters as amount of output data and complexity of user-defined code.
The number of points is defined by product of the resolution in ''x''-, ''y''- and ''z''-direction
 
The number of points is defined by the product of the grid points in ''x''-, ''y''- and ''z''-direction


[[FILE:palm_scaling_n_points.png|170px|center]]
[[FILE:palm_scaling_n_points.png|170px|center]]
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[[FILE:palm_scaling_n_iterations.png|130px|center]]
[[FILE:palm_scaling_n_iterations.png|130px|center]]


with the pyhsical simulation time ''T_{total}'' and the timestep size ''\Delta t''. The timestep size ''\Delta t'' can be estimated over the Courant-Friedrichs-Levy like criteria  
with the pyhsical simulation time ''T_{total}'' and the timestep size ''\Delta t''. The timestep size ''\Delta t'' can be estimated by the Courant-Friedrichs-Levy like criteria  


[[FILE:palm_scaling_delta_t.png|center|250px]]
[[FILE:palm_scaling_delta_t.png|center|250px]]

Revision as of 17:38, 14 January 2013

The software PALM is a large-eddy simulation (LES) model for atmospheric and oceanic flows developed at the Institute of Meteorology and Climatology of the Leibniz Universität Hannover.

Installation

Please download and follow the follwing pdf-document for detailled instructions for the installation of PALM:

SGE scripts

Sample SGE scripts for submitting PALM jobs can be found here:

  • palm_simple.sge (only for simple version of PALM - see installation guide for more information)

Please copy the sample script to your working directory (as palm.sge or <different-name>.sge). For carrying out the test run (to verify the installation), the script does not need to be modified. Please see the installation guide for instructions on how to modify the script for different runs.

Runtime estimation

The runtime of PALM (which is needed for the SGE script and for mrun) can be estimated by

[[1]]

where the constant c_{PALM,FLOW} is approximately

[[2]]

This value is a first guess from a sample of simulation data. However, this number might have to be corrected in the future. It depends on additional parameters as amount of output data and complexity of user-defined code.

The number of points is defined by the product of the grid points in x-, y- and z-direction

[[3]]

The number of iterations can be calculated by

[[4]]

with the pyhsical simulation time T_{total} and the timestep size \Delta t. The timestep size \Delta t can be estimated by the Courant-Friedrichs-Levy like criteria

[[5]]

where L and N are the length of the simulated domain and resolution in x-, y- and z-direction, respectively. The velocity \bar u_{max} is the maximal windspeed of the simulation.

Note: In the time estimation the scaling is assumed to be linear which is not true for large number of used CPU cores and small resolutions (O(10⁵) points/core). In this case the constant could be larger.

Known issues

  • With the Intel Compiler 12.0.0 the compiler flag -no-prec-div and -np-prec-sqrt can lead to different results for same runs. Please don't use these flags. Note that the flags will automatically be set when using the compiler option -fast. In this case you should set -prec-div and -prec-sqrt.

Tutorials

Here are slides from the last training at ForWind in April 2012.

Day 1

Day 2

Day 3


External Links

Retrieved from "https://wiki.hpcuser.uni-oldenburg.de/index.php?title=PALM&oldid=349"