On Normwise Structured Backward Errors for Saddle Point Systems
Hua Xiang, Yimin Wei · SIAM Journal on Matrix Analysis and Applications · 2007
We derive the explicit expressions of the normwise structured backward errors of saddle point systems; we extend the previous results of Sun [Linear Algebra Appl., 288 (1999), pp. 75–88] to a general $2 \times 2$ block linear system, where the (1,1) block is general and not symmetric. We also compare the structured backward error with the unstructured one and find that the difference can be arbitrarily large.