**4. Parallel strategies**

Generally, there are three strategies to implement the parallelism of MPS algorithms, that is, realization-level, path-level, and the node-level parallelization. The bottleneck for large-scale application focuses on the millions' of nodes in the training image and simulation grids. So we present two parallel implementations on node-level for SNESIM and on both node-level and path-level for Direct Sampling in this section.
