At runtime, Darshan detects files that are shared across MPI_COMM_WORLD and reduces them to a single record. It also finds the min, max, and variance of both time and bytes moved for each process.

We do not have the same functionality on partially shared files (ie, files in which only a subset of nodes open the same file). Detecting partially shared files and reducing them may be difficult at run time; we might want to consider building that functionality into darshan-parser.