[apw]

MPI has a reduce operator. On some supercomputers, the operator is implemented in an ASIC.

It is quite easy to implement map/reduce style programs in MPI. It is quite difficult or impossible to implement the parallel algorithms that win the Gordon Bell prize, almost all of which are implemented in MPI, using Hadoop.

[seanmcdirmid]

MPI can't schedule to optimize IO/data shuffling like MapReduce, this is the price for being more general. The biggest competition to MPI in the HPC space is actually CUDA and GPUs. In either case, the data pipeline is exposed to the compiler or run time for optimization, where as MPI everything is just messaging.