I haven’t tried Timefold but did try a ton of solvers (local and web) a few years ago when trying to optimize MRP schedule. One of the hardest parts was converting my business logic into constraints, especially date based calculations.
Instead of explicit constraints, is there a way to provide a calculation that can be minmaxed? If every order has a due date, can I say +/- 3 days = 0, 7 early = 9999 (not allowed), 7+ days late = (days late)^2?
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Somewhat related, I looked at a bunch of solvers for vehicle routing with time windows. One thing that surprised me was that the SaaS-based distance matrix calculations were prohibitively expensive. Google charged $0.01 per matrix element.
How do folks normally get the distance matrix? I ended up just using the Mapbox Optimization API instead of using a solver.
It is always a question of accuracy / convenience. You can start with straight / geodesic distance. One step up is to use open street maps with an offline open source router [1]. But if you want the accurate driving distance with the latest closures / traffic data the big vendors are the only choice.
Take a look at OSRM. For the Timefold Field Service Routing REST APIs, we have a maps service that runs OSRM under hood by default, but supports alternative map providers too. It calculates both travel time and distance matrixes.
Our maps service does do a bunch of additional optimizations (caching, incremental requests, ...) to assist any solver model we run that request maps information.
I've had to solve this in a number of ways. The fastest I've found is to precompute a hash map at a low-granularity (well, update on batch cycle regularly). Graphhopper with OSRM + OpenStreetMap data are useful in this domain, to the point where relatively dense polygons can be mapped on 16 CPU hours in a 100km by 100km block.
The GraphHopper Matrix API has an (IMO) attractive pricing especially for large matrices. The pricing is credit based and for large matrices we do not charge for every matrix cell but instead we only charge "locations*10". E.g. for a 200x200 matrix we only charge 2000 and not 40 000 credits as our underlying algorithm is very efficient (scales nearly linear). And let's say you need this calculation 25 times a day (using the premium package) then this leads to $0.016 for 1000 matrix elements. Of course even cheaper for larger matrices.
And larger packages will furthermore include a volume discount.
You need piecewise linear cost function and auxiliary variables. An experienced practitioner should be able to help you with either mixed integer linear programming or constraint programming
No need when using the timefold solver, the constraint streams allow for a more "human readable" approach.
e.g. Penalise when the minimum is not reached, Penalise when the maximum is exceeded (2 constraints).
I didn't use Timefold but the predecessor Optaplanner, and I remember there were hard constraints which must always be true (eg one room can only be used for one meeting at a given time) and then there were soft constraints which were minimized (eg shorter distance is better)
so an optimization problem can then be described with a set of those hard/soft contraints
Yes!
These days, to handle cases with more work than resources to do it, medium constraints are used a lot too (so hard/medium/soft constaints), to penalize the amount of unassigned work. Those are harder than soft constraints, but softer than hard constraints.
And there is definitely a difference between them. If you try to view a cross view image using parallel view, it will look weird and not be easy to focus. Maybe the egg crate image was different?
Parallel view is easy for me but it takes a bit of effort for me to see cross view. For cross view, I start by looking cross-eyed at my nose and then try to see the image without fully uncrossing my eyes.
I have the opposite experience. Cross view is easy for me but focusing parallel view is very difficult to impossible.
When I try to relax my eyes to look past the screen to start the parallel view (I think that's how it is done?) the image is too blurry to resolve. When I let my eyes adjust that, they fall apart to the separate images.
Thanks for the link, I saw the Tokyo parallel view beautiful crispy for the first time, now I can't do it again, I guess my eyes became tired and need some time
I haven’t played all the games but the recent ones I tried had a historical tour mode where you get to explore day-in-the-life of an Ancient Greek city or Viking village, with people going about their routines working, trading, farming, gathering. With VR it would be the closest thing to time travel we currently have.
And they do have many of the historical landmarks in pretty stunning detail, with drapes and paintings of what it most probably looked like back then.
I learn on and off the job. Everyone benefitted including my past employers when I learned on the job. They weren’t paying me to perform based on my existing knowledge. They were paying me to solve problems and if that meant I needed to learn a new tech or skill, that was their cost of doing business.
I have a number of young devs working for me and I give them the same advice. None them knew how to handle sessions using JWT tokens, use pgvector, or run our containers on Fly.io when they were hired. They learned it on the job, on the clock, and I am so proud of them for it.
I’ve been learning since early 90s and have frankly forgotten more than I remember but none of that matters. What matters to me is if you can solve problems, even if you need a bit of guidance and coaching from others. If your current employer doesn’t feel that way, I hope you can find one that does someday. It is why I am still coding three decades later.
I think it also has to do with how many devices you have on it and how often they update state. I have 300+ IP devices and have to run it on a mini PC because RPi was too slow. No custom plugins or extensions, just a few basic integrations.
I can vouch for Lookeen (circa 2012-2015). I set it up for 200+ users on Citrix and it worked great. I had the index for each user saved to their network share and yet the search was instant. It even indexed shared mailboxes. It barely used any CPU when doing background indexing.
It worked well with thin OSTs too but due to how Outlook and Exchange work, it would have to rebuild the index more often.
Definitely a blast from the past reading the word “Lookeen” but mostly good memories about it. I believe the ADMX integration was pretty decent too.
Absolutely. Pallet arrangements are usually a required spec from the customer to the vendor. The arrangement order matters considerably for shipping and needs to be agreed upon beforehand.
Exactly. It was also my first real job as an IT manager, and I had just setup my first business wifi network for use with a shiny new Windows mobile scanner. So it definitely made me question if I was cut out for it.
I left the company last year, having grown to 700+ employees in pharmaceutical manufacturing, a far-cry from my one-man IT department for 20 employees making shampoo. And while there were many, many weird issues over the years, none was ever so satisfying to resolve.
