The number of threads used during preview and live rendering.
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 2 cores, while threads=2 means only use 2 cores. This is useful when you want to leave one or two cores for other tasks. One example of this is so that Katana can be more responsive while Arnold is rendering in the Render View.
Similar to "threads" this is the number of threads used for batch/disk rendering. Usually you want to use all available threads. This can be overridden when invoking Katana in batch mode with the "–threads3d=" command line parameter.
This is the number of threads KtoA uses when translating the scene. Usually, a handful of threads suffices to give an advantage and making this number higher may actually slow down scene translation.
Particularly for batch rendering, when many frames are launched on the farm simultaneously, Katana may request the same resources on the network all at once from many different machines. This can cause bottlenecks on file servers as the same files (such as Alembic assets) are requested at the same time. Randomizing the order of children locations can help alleviate this problem and improve overall render throughput on a render farm. When not in this situation, it doesn't help to activate this, and in fact it carries a small amount of performance overhead at render startup.
This area shows any arbitrary values set on the root location's arnoldGlobalStatements.arbitrary attribute group. Use an AttributeSet node or opscript to add arbitrary attributes, and they will be written out as user data to the Arnold options node.