Sensitivity Vector

The sensitivity vector, for a given model, is composed of sub-vectors corresponding to sensitivities of resp^calc to multigroup cross sections for a given isotope-reaction pair.
The isotope-reaction pairs form the "isotope-reaction list," whose order must be consistent for all matrix operations.

The isotope-reaction pairs linked to the sub-vectors forms a list called the "isotope-reaction list". This list and its order are important to respect the alignment rule between vectors and matrices.