This is sad news, he invented not only the actor model, but also planner and did a lot of groundwork for deductive and parallel systems.
One of the more obscure things he pursued as a result of his early actor model work was unbounded nondeterminism as a potential source for hyper-computation.[1]
I'll always remember fondly that he pointed me to some papers via twitter when I asked him some questions about unbounded nondeterminism as an undergrad.
If I am reading the footnoted slides properly, do they mean that we are willing to use unbounded determinism when we can take the property that "actions eventually complete" as an axiom (so we prove the rest of the system based on that hypothesis, and make the statistical argument that for those almost never cases where actions don't complete, the process is so unlucky that it "has already been run over by a bus"* anyway, to justify admissability of the hypothesis)?
* thank you Jim Gray (1944-?2007). compare the difference in liveness provability between token ring and ethernet. (but also compare their pragmatic adoption)
I first heard about Hewitt after watching this[0] conversation about the actor model. It's truly a masterclass. For those who want to learn more about the actor model, or simply have a fond memory of ProfHewitt, I highly recommend it.
I've met him at Code Mesh in London in 2018 where he gave a keynote on ultraconcurrency for globally connected intelligent systems [1]
Joe Armstrong was present too, he had a talk later that day and I witnessed a conversation between Armstrong and prof. Hewitt about the actor model after the keynote, it was brilliant.
Sad news. Some of the early papers on actors are listed at http://erights.org/history/actors.html (with a bunch of broken links, unfortunately, but they should be findable).
Dang it, we lost 2 of the biggest champions of the Actor model, Carl and Joe a couple of years ago. Who is left to carry the torch to illuminate millions of developers who have no idea or have never heard of the Actor model? Sadly, we will see thousands or poorly thought out replacement models (eg. C++ futures, thread pools etc), which only offer a subset of Actor functionality instead of implementing the whole she-bang. E
All Mac and iOS developers will eventually be exposed to it. Swift's concurrency support is based on the actor model and has a construct named "actor," which does what it says on the tin.
This is a real loss. I learned a lot from him, ironically more from late night trips to Chinatown than formally in the lab. He had a wide ranging intellect that did not diminish with age.
It is a real loss, Gumby. Carl and I were friends and spent hours on the telephone solving the problems of the world and playing polymath math. Hardly a day would go by without an hour or so chat with Carl.
The actor model is simply magnificent. Once i encountered the actor model, concurrency just clicked for me. Even writing concurrent programs in a non-actor context became simple and easy. It is that amazing.
Every so often when thinking about a system I find I need a default model to go back to. Like when a system seems to be complex or someone is claiming that it has some new property that makes it exceptional or whatever. It's probably possible to pick a few different models but I find the actor model usually covers it. e.g. "Well when you really look at it, it's just a bunch of actors sending messages to each other's addresses/mailboxes"
My very first computer as an HP. My dad came home with one from CompUSA back in the mid-90s. I think this was shortly after Packard Bell rebranded themselves. I don't know what involvement Carl had with the company by that point in time, but he indirectly had an impact on me as it got me started in computers very early in life. RIP.
One of the more obscure things he pursued as a result of his early actor model work was unbounded nondeterminism as a potential source for hyper-computation.[1]
I'll always remember fondly that he pointed me to some papers via twitter when I asked him some questions about unbounded nondeterminism as an undergrad.
[1]: https://programme.hypotheses.org/files/2019/06/cardone_dayli...