On the strong convergence of sequences of Halpern type in Hilbert spaces

In this paper, we introduce a concept of A-sequences of Halpern type where A is an averaging infinite matrix. If A is the identity matrix, this notion become the well-know sequence generated by Halpern's iteration. A necessary and sufficient condition for the strong convergence of A-sequences of Halpern type is given whenever the matrix A satisfies some certain concentrating conditions. This class of matrices includes two interesting classes of matrices considered by Combettes and Pennanen [J. Math. Anal. Appl. 2002;275:521-536]. We deduce all the convergence theorems studied by Cianciaruso etal. [Optimization. 2016;65:1259-1275] and Muglia etal. [J. Nonlinear Convex Anal. 2016;17:2071-2082] from our result. Moreover, these results are established under the weaker assumptions. We also show that the same conclusion remains true under a new condition.