“…The emergence of parallel computing has also triggered a significant effort toward automatic generation of scalable CC codes, which resulted in the development of specialized systems that integrate elements of symbolic algebra for manipulating and optimizing tensor expressions with efficient parallel tensor libraries. Specialized distributed-memory (or in some cases sharedmemory) libraries for automatic tensor blocking, tensor redistribution, and efficient utilization of tensor symmetries such as Tensor Contraction Engine (TCE) 194,195 , super instruction assembly language (SIAL) 110,196 , libtensor 197 , Cyclops Tensor Framework (CTF) [198][199][200] , and TiledArray (TA) 201 play a key role in enabling high-accuracy CC methods in many community codes including NWChem 202 , Aquarius 203 , CFOUR 204 , MPQC 38 , Q-Chem 39 , ACES 24 , and MRCC 205 . Below, three of these tensor packages, TCE, TAMM, and TA are discussed as relevant to the NWChem (TCE) and NWChemEx (TAMM and TA) packages.…”