@TechReport{ BeuHofer16, author = {Beuchler, Sven and Hofer, Katharina}, title = {Additive Schwarz solvers for $hp$-FEM discretizations of PDE-constrained optimzation problems}, institution = {INS}, year = {2016}, optkey = {}, opttype = {}, optnumber = {}, optaddress = {}, optmonth = {}, note = {also avaiable as INS-Preprint 1625}, inspreprintnum= {1625}, annote = {submitted}, pdf = {http://beuchler.ins.uni-bonn.de/research/INS1625.pdf} }