* TAPIOCA_BUFFERSIZE = Buffer size in bytes. Use a multiple of the file system block size to avoid lock contention. Two allocations of this buffer size will be made to perform double-buffering
* TAPIOCA_COMMSPLIT = true / false. If true, MPI_Comm_split will be used to create one sub-communicator per aggregator. If false, the sub-communicator will be created from MPI_Groups. In the case of a single shared file as output on a large-scale run, set this variable to false can divide by two the time needed to elect the aggregators.
* TAPIOCA_DEVNULL = true / false. If true, instead of effectively writing the file, the write operation is made in /dev/null. Useful for aggregation time measurements.