RUNNING JOBS WITH GPU
- fluent command runs ANSYS Fluent interactively
- -g indicates that the program is to be run without the GUI or graphics
- <version> specifies the 3d or 3ddp version of ANSYS Fluent
- <nprocs> specifies the total number of CPU processors across all machines/nodes
- <ngpgpus> specifies the number of GPUs per machine/node available in parallel mode. Note that the number of processes per machine must be equal on all machines and ngpgpus must be chosen such that the number of processes per machine is an integer multiple of ngpgpus. That is, for nprocs solver processes running on M machines using ngpgpus GPUs per machine, we must have:
- (nprocs) mod (M) = 0
- (nprocs/M) mod (ngpgpus) = 0
- <journal_file_name> specifies the name of the journal or input file.
- <output_file_name> specifies the name of the output file. It is a file that the background job will create, which will contain the output that ANSYS Fluent would normally print to the screen (for example, the menu prompts and residual reports).
Journal File contains sequence of ANSYS Fluent commands that are identical to those that you would type interactively. Comments can be added in the file with a semicolon at the beginning of the line.
MODEL SUITABILITY FOR GPU ACCELERATION
A coupled solver benefits most from GPUs. In flow only problems, typically the coupled solver spends about 60 percent to 70 percent of its time solving the linear system using AMG, making GPUs a good choice. Since the segregated solver spends only 30 percent to 40 percent of its time in AMG, GPUs may not be advantageous because of memory transfer overhead costs. By default, GPU acceleration is applied automatically to coupled systems and not to scalar systems because scalar systems typically are not as computationally expensive. However, if desired you can enable/disable GPGPU acceleration of the AMG solver for coupled and scalar systems with the following text command and list each supported equation type allowing you to enable/disable GPGPU acceleration, choose between AMG and FGMRES solvers, and specify various solver options.
- The population balance model is active.
- The Eulerian multiphase model is active.
- The system has more than 5 coupled equations.
ACCELERATING DISCRETE ORDINATES (DO) RADIATION CALCULATIONS
The solver is based on OpenACC and can run on either architectures: CPUs or GPUs. The solver is currently not compatible with all the models and boundary conditions but is found to be extremely fast where applicable. Cases that need very high resolution in discretizing the radiation intensities benefit the most from this accelerated solver. Head lamp simulation is one such application area where the accelerated solver speeds up the computation by several times.
After you have selected the DO model in the Radiation Model dialog box, you can enable the accelerated DO solver by using the following text command:
The accelerated DO solver is incompatible with some models and settings; when necessary, Fluent will automatically revert to the standard DO solver when the calculation is started and print a message about the conflict.
If you plan to use GPUs with the accelerated DO solver, it is recommended that you run NVIDIA’s multi-process server (MPS) before launching ANSYS Fluent using the following command:
When using the raytracing_acc utility from outside an ANSYS Fluent session, the command line is
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