Jip J. Dekker

@[email protected]
30 Followers
207 Following
277 Posts
OPTIMA Research Fellow working on Programming Languages & Optimization at Monash University, Melbourne, Australia. A developer of the MiniZinc language .
Apart from work, I also post about music, birds, cycling, cricket, and other things I like.
(Searchable)
Pronounshe/him
LanguageEnglish & Nederlands
Websitehttps://dekker.one
ORCIDhttps://orcid.org/0000-0002-0053-6724
Show threadJip J. DekkerNov 21, 2023
@b0rk to understand the difference it might also be interesting to read about the alternative: Pijul is a SCM where commits are diffs https://pijul.org/
Pijul

An easy to use, distributed and fast version control system.

Show threadJip J. DekkerNov 21, 2023
@waywardmonkeys yes, it’s often hard to balance research and software development. Although I don’t want to give the impression that no developing is happening at the moment. It’s really that we are thinking about some larger revamping of chuffed so it is hard to make time for these type of engineering tasks at the same time.
Show threadJip J. DekkerNov 20, 2023

@waywardmonkeys As some general hints, I would probably like to see it as part of the same repository to make sure that we can easily detect changes that conflict between the code bases.

Also, it is noteworthy that Chuffed currently uses global variables, which is why it is not great for using as a library. You probably would want to investigate whether this is a problem for your use cases.

Show threadJip J. DekkerNov 20, 2023
@waywardmonkeys Although I would be happy with Chuffed bindings in Rust, I think we would need them to be in a relatively complete state before we would put them publicly in the chuffed organisation. We are lacking on development time, so we would need to know that it would be supportable before we can make it part of the organisation.
Jip J. DekkerNov 17, 2023

#MiniZinc 2.8 has been released. No big new language features, but it does include a lot of improvements to make your life easier:

- #ORTools is now part of the MiniZinc bundle.
- #HiGHS now provides intermediate solutions.
- Experimental support for propagator based meta-search, such as LNS variants.
- Commutative CSE
- Support optional version of global_cardinality, increasing, and count globals.

Find more details and many other improvements in the change log: https://www.minizinc.org/doc-2.8.0/en/changelog.html#v2.8.0

MiniZinc Change Log — The MiniZinc Handbook 2.8.5

Jip J. DekkerNov 10, 2023
Natasha  🇪🇺Nov 9, 2023

I recently heard about this novel in which Schrodinger's cat and Pavlov's dog team up for an epic adventure, so I went down to my local library to see if they had a copy

The librarian said that my description of the book rang a bell but she wasn't sure if it was there or not ...

Jip J. DekkerNov 9, 2023
Rob Thomas [Admin m.au]Nov 8, 2023

A bit of an unofficial post-mortem on #Optus #outage yesterday (please BOOST for visibility!) I have no insider knowledge, all I can do is look at what Optus's networking gear told the rest of the world through #BGP, and make some informed guesses based on that.

The problem yesterday started at about 4am, when Optus told the world 'I no longer have any internet connectivity', and 'Do not send any internet traffic to me, at all'. The technical description is that they withdrew ALL of their routes from the #DFZ (Which is "The Internet", as seen by all the core routers that ACTUALLY control the internet).

However, as a precursor at about 3am there was a hint that things weren't perfect, as there was a flurry of changes from Optus to the outside world saying, roughly, 'Something has changed inside my network, but you can still keep sending me stuff'.

Now, as two final bits of possibly relevant information, the default for maximum-prefix on #Cisco #ASR9000 is 1048576 (this number is 'the number of routes that can be accepted by this router'), and MOST IMPORTANTLY the DFZ ("the internet") has about 980,000 routes in it at the moment. That's only 90k odd routes LESS than the default maximum.

I'd be amazed if Optus has less than 100k internal routes that aren't visible to the internet, but are visible internally.

So here's what I think happened. The at 3am, the first core #router was upgraded, and a new config was put in place. This did not join the network correctly, and things were half broken. What SHOULD have happened is that all the changes should have stopped, and either rolled back, or waited for further investigation (the cause being that more than 1mil routes were visible, causing it to shut down)

However, someone decided 'Well, maybe if we upgrade the SECOND one, that'll fix the first one' at 4am. That broke the SECOND one, and took Optus completely off the internet.

(Continued, see next for why this is far worse than it should have been)

Show threadJip J. DekkerOct 22, 2023
@janeadams Welcome to Melbourne! 🦘🇦🇺
Jip J. DekkerOct 16, 2023
Holly KirkOct 15, 2023

Dunno about you, but an everyday dose of nature is what I need right now! And the #aussiebirdcount starts today!

It's easy to take part - download the app, watch for 20 minutes, count any birds...
Repeat as needed.
Like medicine.
🪶🌿🐦💊🦜🌏🧪
https://aussiebirdcount.org.au/

Aussie Bird Count

Celebrate National Bird Week by taking part in the biggest citizen science project to hit Aussie shores. Join thousands of people from across the country, heading out into their backyards, local parks or favourite open spaces to take part in the Aussie Bird Count.

Aussie Bird Count
Jip J. DekkerOct 15, 2023
Conor Mc BrideOct 14, 2023

The thing about arithmetic is that computers are good at it. The point is to figure out what is the good arithmetic to tell the computers to do.

School mathematics has not caught up with this fact. It trains people to do computer-replaceable things, and actively disables the parts of brains that explore.

I don't blame the teachers: I blame the testers.