  Networks-on-chips (NoCs) have become the mainstream communication
infrastructure for chip multiprocessors (CMPs) and many-core systems. The
commonly used parallel applications and emerging machine learning-based
applications involve a significant amount of collective communication patterns.
In CMP applications, multicast is widely used in multithreaded programs and
protocols for barrier/clock synchronization and cache coherence. Multicast
routing plays an important role on the system performance of a CMP. Existing
partition-based multicast routing algorithms all use static destination set
partition strategy which lacks the global view of path optimization. In this
paper, we propose an efficient Dynamic Partition Merging (DPM)-based multicast
routing algorithm. The proposed algorithm divides the multicast destination set
into partitions dynamically by comparing the routing cost of different
partition merging options and selecting the merged partitions with lower cost.
The simulation results of synthetic traffic and PARSEC benchmark applications
confirm that the proposed algorithm outperforms the existing path-based routing
algorithms. The proposed algorithm is able to improve up to 23\% in average
packet latency and 14\% in power consumption against the existing multipath
routing algorithm when tested in PARSEC benchmark workloads.
