For some iterative algorithms we can create procedures to parallelize them. This parallelization involves a Map step (when you slice the data between the nodes) and the Reduce step (when you reduce/gather some data from the node). And you do this (Map/Reduce) several times.

To implement that using platform, you need two blocks, one for the Map and one for the Reduce. Since the flow of the data in the platform is just forward, it is not possible to do a loop between these two blocks

Would be nice to have that feature.