+\subsection options_model_nthreads Parallel threads for model updates
+
+By default, Surf computes the analytical models sequentially to share their
+resources and update their actions. It is possible to run them in parallel,
+using the \b surf/nthreads item (default value: 1). If you use a
+negative value, the amount of available cores is automatically
+detected and used instead.
+
+Depending on the workload of the models and their complexity, you may get a
+speedup or a slowdown because of the synchronization costs of threads.
+