TL: added hans's summary for serial bottlenecks

Author: tlunet

_events_past/2025-14th-pint-workshop.md

@@ -46,7 +46,7 @@ Please visit the [conference website for more information.](https://icms.ac.uk/a
 
 #### Full Summary
 
-- Redundant computation ([Hans](https://crd.lbl.gov/divisions/amcr/computational-science-dept/anag/about/staff-and-postdocs/hans-johansen/) to summarize).
+- [Hans](https://crd.lbl.gov/divisions/amcr/computational-science-dept/anag/about/staff-and-postdocs/hans-johansen/) asked about removing serial bottlenecks for any coarse operators. In other fields, redundant computation is used to remove latency and improve scaling. In (space) MG methods consolidation is another technique. [Josh](https://github.com/JHopeCollins) suggested wavefront-type methods, and [Rob](https://people.llnl.gov/falgout2) commented this is just changing the constant for an already O(N) method. There was a suggestion to develop performance models like what [Daniel](https://github.com/danielru) had presented in his talk.
 - [Martin](https://www.unige.ch/~gander) cautioned against the use of the word “optimal” without more specific information - this comes from the DD community where it really means “mesh independent scaling”.
 - Does PinT work for hyperbolic problems? See [Martin’s Acta Numerica paper](https://www.cambridge.org/core/services/aop-cambridge-core/content/view/E580B25A44766E6729A65D7AF05B1198/S0962492924000072a.pdf/time_parallelization_for_hyperbolic_and_parabolic_problems.pdf) - there are many methods that are not multilevel that can work. Multilevel is a challenge.
 - [Josh](https://github.com/JHopeCollins) pointed out a common subproblem shared by ParaDiag and REXI methods: solution of systems that look like backwards Euler steps with complex timestep (which [Colin](https://github.com/colinjcotter) clarified lead to an indefinite-Helmholtz-like problem on elimination to one variable).