The letters can just be walked next door. In essence, it is as if these mesh pairs are neighbors and need not send mail to each other via the postal system. Why would you do this? Suppose you only have four processors available for this job.īy starting only four processes instead of six, you can save time because ‘mesh2’ and ‘mesh3’ can communicate directly with each other without having to transmit data using MPI calls over the network. Note that the processes need to be invoked in ascending order, starting with 0. In this case, only four processes are to be started, numbered 0 through 3. The parameter MPI_PROCESS instructs FDS to assign that particular mesh to the given process. However, it is possible to assign more than one mesh to a single process, and it is possible to assign more than one process to a single processor.Ĭonsider a case that involves six meshes: Usually in a MPI calculation, each mesh is assigned its own process, and each process its own processor. The most relevant part of that section is quoted below for reference. More information about the MPI_PROCESS and N_THREADS parameters on a MESH record, can be found in section 6.3.3 entitled 'multiple Meshes' of the FDS User’s Guide. This feature allows for any number of meshes to be assigned to the same processor simultaneously to improve calculation efficiency. Most modern computers have multiple 'cores' or 'threads' per processor, and through the Message Passing Interface (MPI) feature, FDS allows for each mesh to be assigned to a specific thread using the MPI_PROCESS keyword. In many cases, multiple meshes of different resolutions are required to accurately define the computational domain of the simulation. To describe this computation volume, one or more subsections of the overall volume are referred to as a 'mesh', and defined by a &MESH entry in the input file.

Introductionįor typical building design calculations using the Fire Dynamics Simulator (FDS), a large volume of space will be simulated. To follow along with this tutorial and test this feature for yourself, download the relevant example files here. Created with software version: 2020.1 Table of Contents

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