CUDA: Difference between revisions

The following program will add two numbers together on a GPU. Save the file as <code>add.cu</code>. ''The <code>cu</code> file extension is important!''.  

To run the program, create a Slurm job script as shown below. Be sure to replace <code>def-someuser</code> with your specific account (see [[Running_jobs#Accounts_and_projects|accounts and projects]]). For options relating to scheduling jobs with GPUs see [[Using GPUs with Slurm]].  

Submit your GPU job to the scheduler with this command.

</source>For more information about the <code>sbatch</code> command and running and monitoring jobs see [[Running jobs]].

If you run this without a GPU present you might see output like <code>2+7=0</code>.  

To learn more about how the above program works and how to make the use of a GPUs parallelism see [[CUDA tutorial]].

=== "Compute Capability" === <!--T:50-->

NVidia has created a technical term "compute capabilty" which they describe as follows:

The ''compute capability'' of a device is represented by a version number, also sometimes called its "SM version". This version number identifies the features supported by the GPU hardware and is used by applications at runtime to determine which hardware features and/or instructions are available on the present GPU."  ([https://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#compute-capability CUDA Toolkit Documentation, section 2.6])

The following errors are connected with "compute capability":

If you encounter either of these errors, you may be able to fix it by adding the correct FLAG to the <code>nvcc</code> call:

where “XX” is the "compute capability" of the Nvidia GPU that you expect to run the application on.  

To find the value to replace “XX“, see the Available Hardware table on the page [[Using GPUs with Slurm]].

'''For example,''' if you will run your code on a Narval A100 node, its "compute capability" is 80.

The correct FLAG to use when compiling with <code>nvcc</code> is