Major new release of ITensor. While the interface is mostly backward compatible with version 1.3.x, the internals of ITensors and IQTensors have been significantly redesigned. Major overhaul of ITensor and IQTensor storage. New loosely coupled design where storage is managed by objects which can have arbitrary data layouts. Storage objects are manipulated by overloads of a function named doTask, which supports a type of multiple dispatch (similar to function overloading but determined at run time instead of compile time). For more information read the article on the ITensor website. Complete redesign and rewrite of the matrix library underpinning ITensor. New TensorRef library provides a basic tensor interface, of which matrix and vectors are a special case. For the complete set of changes, see the changelog on the ITensor website.