Use the Arnold Denoiser imager when rendering a single frame.
Use an optimal number of threads based on the number of hardware processing cores.
If autodetect is disabled, this will let you manually set the number of threads used by the denoiser. Negative numbers are also allowed. If specifying 0 threads means use all cores on a machine, then negative numbers can mean use all but that many cores. For example, threads=-2 means use all but two cores, while threads=2 means only use two cores. This is useful when you want to leave one or two cores for other tasks. One example of this is so that Cinema 4D can be more responsive while the images are denoised in the background.