115.fds4
SPEC MPI2007 Benchmark Description

Benchmark Name

115.fds4

Benchmark Author

Kevin McGrattan kevin.mcgrattan@nist.gov

Benchmark Program General Category

FDS is a finite difference CFD model

Benchmark Description

FDS is a computational fluid dynamics (CFD) model of fire-driven fluid flow. The software solves numerically a form of the Navier-Stokes equations appropriate for low-speed, thermally-driven flow with an emphasis on smoke and heat transport from fires. Smokeview is a visualization program that is used to display the results of an FDS simulation.

MPI Usage

This code uses MPI_ALLGATHER for communication with a smattering of MPI_SEND and MPI_RECV. Synchronization is primarily MPI_BARRIER and MPI_WAITALL. The code supports all jobs sizes between 4 and 512. It does not step down the MPI_COMM_SIZE in order to support this range of sizes.

Input Description

The CPU time for any given "GRID" is roughly proportional to the number of grid cells (IBAR * JBAR * KBAR). All your GRIDs are 25 * 25 * 25, meaning that the overall CPU time will not be improved. Here's how to approach it -- consider the unit cube, and decide how fine a grid you want to use to discretize it. For simplicity, assume that your grid cells are to be perfect little cubes. Suppose you want to break the 1 m by 1 m by 1 m domain into 2 cm cells.

One mesh case (1 CPU): IBAR=50,JBAR=50,KBAR=50

two mesh case (2 CPU): IBAR=25,JBAR=50,KBAR=50
                       IBAR=25,JBAR=50,KBAR=50

four mesh case(4 CPU): IBAR=25,JBAR=25,KBAR=50
                       IBAR=25,JBAR=25,KBAR=50
                       IBAR=25,JBAR=25,KBAR=50
                       IBAR=25,JBAR=25,KBAR=50

The total number of cells in the unit cube remains the same, but the respective meshes are getting smaller. Notice that the sub-domains are the same size and have the same number of cells. That's helps with load balancing. This is a time dependent calculation, and if the meshes have unequal numbers of cells, those with the fewer will idle waiting for those with more.

Output Description

a text file named fds4.out which describes Miscellaneous Parameters and Surface Conditions

Programming Language

Primary Fortran90 with 2 C support files

Known portability issues

Version and Licensing

This benchmark was ported from version FDS 4.02 August 13, 2004

References

http://fire.nist.gov/fds

Last updated: February 2, 2007

115.fds4 SPEC MPI2007 Benchmark Description