Hello everyone! I asked the following question and think I might get some suggestions whether what I want is doable or not.
https://stackoverflow.com/questions/53746046/how-can-i-implement-zipwithindex-like-spark-in-apache-beam/53747612#53747612 If I can get `PCollection` id and the number of (contiguous)lines in each `PCollection`, then I can calculate the row order within each partition/`PCollection` first and then do prefix-sum to compute the offset for each partition. This is doable in MPI or openMP since I can get the id/rank of each processor/thread. Best, Chak-Pong
