How do I compare the performance on GPUs vs. CPUs?

To see the performance difference of running on GPU over CPU, manually switch where your queries are run:

1. Enable timing reporting in heavysql using \timing
2. Ensure that you are in GPU mode (the default): \gpu
3. Run your queries a few times. Because data is lazily moved to the GPUs, the first time you query new data/columns takes a bit longer than subsequent times.
4. Switch to CPU mode: \cpu Or add the g_cpu_mode hint to the query and run your queries a few times.
5. Compare the different runtimes.

If you are using a large data set, you should see a significant difference between the two. However, if the sample set is relatively small (for example, the sample 7-million flights dataset that comes preloaded in OmniSci), some of the fixed overhead of running on the GPUs causes those queries to appear to run slower than on the CPU.