  We propose Atomic Active Messages (AAM), a mechanism that accelerates
irregular graph computations on both shared- and distributed-memory machines.
The key idea behind AAM is that hardware transactional memory (HTM) can be used
for simple and efficient processing of irregular structures in highly parallel
environments. We illustrate techniques such as coarsening and coalescing that
enable hardware transactions to considerably accelerate graph processing.We
conduct a detailed performance analysis of AAM on Intel Haswell and IBM Blue
Gene/Q and we illustrate various performance tradeoffs between different HTM
parameters that impact the efficiency of graph processing. AAM can be used to
implement abstractions offered by existing programming models and to improve
the performance of irregular graph processing codes such as Graph500 or Galois.
