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Writing a Planner to solve a tricky programming optimization problem (rwmj.wordpress.com)
62 points by iamtechaddict on Dec 14, 2013 | hide | past | web | favorite | 13 comments



A smarter approach would be just to use one of the highly optimized ones that exist already ... I use popf, which supports numerics among other things:

http://www.inf.kcl.ac.uk/staff/andrew/popf.html

You just have to write a problem and domain file which is very easy LISP syntax, it's standardized too[1], so you can swap planners later. I can give you examples if you want.

[1] http://en.wikipedia.org/wiki/Planning_Domain_Definition_Lang...

disclaimer: I am collaborating with Maria Fox's group


"Smarter" is a pretty judgmental term.

I know we live in the era of "there already is a library for everything", but for small problems it may still sometimes make sense pick from the ideas you like and code directly. This can take less time than learning whatever huge family of encodings committees have agreed on, is less likely to bring in cross language calling requirements, less likely to bring in specific system requirements and less likely to bring in licensing requirements.


popf is a UNIX command line program. There is no cross-language linking required.

It's been battle tested, all the issues in the article are solved (proper pruning, optimal results). Furthermore, its likely to have less bugs than the authors.

Its been tuned over years for use in competitions. So it probably runs faster than the author's, even though it has more features.

It uses a derivative of the same language the author has suggested (STRIPS is the predecessor to PDDL). So its basically the same interface but more general purpose. Using a standardised language makes the overall system more maintainable

There are no licensing requirements, because its a shell script. If you want to modify the solver then its GPL, but you want to pipe data out of it its ok to invoke it in a separate process.

I agree programming stuff is useful for learning. But optimization is specialised and tangential to most companies core competencies. Leave it to the professionals. You don't write your own SQL query interface for example (which is quite a similar problem).

EDIT:

The author should not feel like they made an obvious mistake though. The planning community is the worst for writing their software up in human readable form. Its really very easy to use, but you would not be able to guess that from their websites, their constant use of complex logical constructs every other sentence is infuriating.


> Its been tuned over years for use in competitions. So it probably runs faster than the author's, even though it has more features.

For OP's use case, which appears to have a max depth of maybe 3, invoking a shell program is going to be a LOT slower than just running the search. No matter how slowly it is implemented.


"Those who don't understand Unix are condemned to reinvent it, poorly." – Henry Spencer

You are basically saying the whole UNIX philosophy of specialised reusable programs chained together is a flawed design.

Spawning a program is not slow. Store the programs file arguments on a ramdisk to avoid disk IO and there will be no noticeable overhead.


Are you kidding me? This is pretty fucking arrogant. My $DAYJOB is FreeBSD kernel hacking.

Reusable piped programs are great for some things, especially a productive shell language. No, composing processes is not great for all things, and certainly not where performance is required. This is why FreeBSD is a monolithic kernel instead of a microkernel with processes, for example.

Spawning a program is incredibly slow, even ignoring disk read times, compared to 3 levels of low-branch-factor search in any language.


Your suggestion is the morale equivalent of asking to install Oracle for a simple "tiny data" database problem when sqlite or just a hand crafted table is far enough.


Writing planners can be fun. If you are interested in the topic (and the advances in the 40 years since STRIPS), you might enjoy the corsera course which starts in a month: https://www.coursera.org/course/aiplan

I wrote a litte strips planner for the last iteration of the course and set it the task to sort some boxes in an interactive box2d world without actually understanding the simulated physics, the result can be quite amusing, http://fhars.github.io/boxworld/


It's nice to see something like this, when programming in startups today involves a lot hand waving about efficiency and a "fuck it, ship it" attitude.


Vaguely disappointed, I thought that this would be an implementation of PLANNER. Still cool though.


Can you give a link to what you're talking about? Searching for "PLANNER" without any extra context seems futile.


The PLANNER system is a similar system that is heavily referenced in the AI literature of the 70s/80s. PLANNER was a tool that let you (handwaving starting) specify a world, transitions for the world state, and then spcify an end goal. PLANNER would find the way to go from start to goal. Prolog is a weakened form of PLANNER, if I understand my AI history correctly. If you rummage around the "Good Old Fashioned AI" history, you'll get a good feel for what it can do.

A technical write-up is available here: http://dspace.mit.edu/handle/1721.1/6916


Wikipedia's disambiguation pages are good for things like this. I found this: https://en.wikipedia.org/wiki/Planner_programming_language




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