While island based parallelism is doable and works reasonably well for many workloads, it's possible to dynamically batch constraints based on their involved bodies such that no constraints in a given batch share the same bodies. All constraints within each batch can be solved in parallel.
Of course, pathological cases can generate a ton of batches. Usually such implementations will use a final 'catchall' batch of some kind after N normal batches. That final batch can be handled sequentially or with a fully parallel jacobi-ish solver (which typically has worse convergence than PGS/SI, but it's usually not a problem in context).
Of course, pathological cases can generate a ton of batches. Usually such implementations will use a final 'catchall' batch of some kind after N normal batches. That final batch can be handled sequentially or with a fully parallel jacobi-ish solver (which typically has worse convergence than PGS/SI, but it's usually not a problem in context).