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Show HN: Science and math-flavored programming problems for beginners (projectlovelace.net)
369 points by PolarizedPoutin on April 17, 2021 | hide | past | favorite | 73 comments

Really nice! When I was in college we had all sorts of online systems that automatically graded assignments based on how close to the correct answer your supplied answer was. I think it'd be nice if in the future there was more of an overlap between science classes and programming classes (almost like a freshman / junior level scientific computation class) where instead of approaching problems from a pure theoretical perspective, we involved these types of computational approaches in parallel. Personally I have found that while I often know how to perform various theoretical computations, it's faster for me to just throw together a quick script to approximate the result (e.g. what's the expected value of the product of two gaussians?)

I agree 100%. It seems that almost any real-world science problem these days requires a computational solution/approach at some level. Taking a computational approach in parallel would be super useful.

Just like the "Structure and Interpretation of Computer Programs", there exists a "Structure and Interpretation of Classical Mechanics".

I think you might enjoy it. Visit- https://en.m.wikipedia.org/wiki/Structure_and_Interpretation...

Or give the exercises a try in the browser, using the Clojure(script) port! It’s a lovely book.


I'm seeing a "404 Not Found" when I visit (after logging into NextJournal).

Very cool! Didn't know there was a classical mechanics counterpart to SICM. Could inspire some new problems for the website.

I agree. I wish school would have merged things like space and programming. I would have been really into it.

This was sort of how physics classes at my alma mater worked. Especially at the upper-division level, it was pretty much expected that you would be submitted a Mathematica notebook with all your homework/tests/labs

It would be so wonderful if Mathematica was a public good.

It is already mentioned in Project Lovelace's About page, but people who like this and Project Euler may also like Rosalind, which is a programming problem site focused on bioinformatics and adjacent algorithms.

I like the eclectic selection of problems. I wish I had seen something like this when I was growing up; a manageable set of problems with the hint of depth.

It’s easy to snipe a nerd, but nerd sniping a non-nerd.. That’s gold.

FWIW: - No margins on the side on iPhone in portrait. - Math formulas are clipped on the top in landscape.

Haha thanks for taking a look!

Ah I'm no web dev so must have missed that margin issue. Was able to reproduce in tablet mode. Thanks for pointing it out!

Very nice curated set of problems with an extremly low entry barrier!

Just would appreciate golang support, but i guess you will get feature requests for all languages anyways :)

Thanks for checking it out!

I don't use Go so might take a while unless someone decides to swoop in and add support for it!

Supporting new languages takes some effort since we need to be able to run arbitrary Go code and communicate with Python. Definitely possible but requires some familiarity with both.

So far we've just been adding languages we know and use. Hoping to learn Rust soon so that might be the next language!

One of the big reasons Project Euler is so brilliant is that every problem is formulated so that you can do it in any language. (I've introduced myself to about six languages this way, none of which you support yet.) What drove the decision to have an allowlist of languages? If you're concerned about people publishing the one true number that is the answer to problem 11, you could always generate random test cases and ask the user to supply the answers to those test cases.

Right yeah it's a good question.

I think the reason we did it is so that we could visualize user output/solutions. You can learn new things by looking at your solutions to various test cases!

One example would be if you submit a solution (or just the code stub) to the Exponential growth problem, then your solution gets plotted and compared with the analytic solution and the correct solution: https://projectlovelace.net/problems/exponential-growth/

Also, unlike Project Euler where every solution is a number, a lot of scientific problems have solutions that are multi-dimensional arrays or multiple objects. So in this case, copy pasting your output becomes quite messy.

It's not trivial to add support new languages since the engine app that runs user-submitted code needs to be able to run arbitrary code in your chosen language and needs a way to communicate with Python (either directly or through JSON passing).

So far we've just been adding support for languages we know and use.

But indeed there are hundreds of languages out there that would be nice to support in some way. It might be neat to add a new submission mode where you're given a couple of test cases that you run manually then submit your solution manually.

For multiple items, you could sum them like in Advent of Code.

Oh that's a neat idea. I should check out Advent of Code. Summing would probably work for a lot of problems but some problems mix strings with numbers in the output

The downside with Project Euler, though is that you need to run your code elsewhere. That's why something like leetcode is so nice (I think, at least): you can run the code right there in the browser. If you take this approach, you're forced to whitelist languages.

Porque no los dos? Allowlist the languages you understand, also allow manual entry for the languages you don't? Seems like the obvious solution.

Could you add Fortran as a programming language? It is one of the main languages for "science and math flavored programming problems". Gfortran is a free compiler that is part of gcc.

That is true. It's not super easy to add new languages and I'm not familiar with Fortran (thankfully our group switched from Fortran to Julia recently!) but we already support C since it's easy to call C from Python. Perhaps Fortran support won't be super hard either.

Really nice! I noticed however that the verification email that gets sent to you after you register has the name/address of 'webmaster@local' rather than <username>@projectlovelace.net.

Speaking of registration, it would be nice if we could log in using our Google accounts (ie. Sign in with <service>), rather than make another account with your site.

Also it would be nice if the site picked up your preferred language of choice after you've done at least one of the problems. I like coding in javascript, but I have to select it from the dropdown list each time I go into a problem to solve, and sometimes I forget to do so (defaulting to Python instead)

Suggestion: allow entering the registered email ID in the place of username, when logging in. I was repeatedly trying to login and even reset the password, assuming the Username field was "Username or Email ID" like it is in many places now. This is certainly a bit of PEBKAC, but it would be a nice usability improvement to allow what's now become a common pattern and make either username or email ID work in that part of the login form.

Thanks for the suggestion! I'm all for quality of life improvements. Definitely wouldn't be hard to add I think.

I implemented the Babylonian square root problem using a simple "x to the power of 0.5" and it accepted the answer!

Yeah haha, this is somewhat intentional!

We thought it would be tedious to write tons of code to make sure users don't take the easy way out for each problem and language, so we figured we might as well allow it. We can't force users to solve the problem our way.

This is fantastic, I actually independently gave my CS101 (for engineers) students some of the same questions last semester (temperature, definite integrals, game of life). Can't wait to try some of these out!

Love this! Always been a fan of kata-type websites like [0], but they all become uninteresting after a while (new katas get bland). This submission has good fresh energy!

[0] - codewars.com

Haha thanks! Didn't know about codewars.com, will look into it. Might be a cool way to learn Rust syntax.

I got completely obsessed with the code golf part at codewars, at some point I just decided enough is enough and stopped playing with. A lot of fun though.

It is neat. The inline math formulas are not displaying right (unless raw latex is right...). Compared to Euler I think perhaps the early problems are a little too easy...

Thanks for checking it out! Will look into the LaTeX rendering issue.

Yeah maybe we went a little too easy on the earlier problems but there will be plenty of harder problems coming up hopefully!

I actually think Project Euler gets hard pretty quickly but I'm no number theory wizard haha.

These problems look like a lot of fun! Unfortunately, I'm currently learning Rust and would prefer to use it to solve these problems.

It would be nice to support uploading a binary or solution (like project Euler) or a CSV of test cases next to solutions. Maybe I'll try compiling rust to c and upload the c file

I'm excited to learn Rust actually so we might support it soon!

It's not trivial to add support new languages since the engine app that runs user-submitted code needs to be able to run arbitrary code in your chosen language and needs a way to communicate with Python (either directly or through JSON passing).

So far we've just been adding support for languages we know and use.

But indeed there are hundreds of languages out there that would be nice to support in some way. I'm gonna think about how we can add a new "submission mode" where you're given a couple of test cases that you run manually with any language then submit your solution.

You could do the problems in rust, locally, and bask in the glow of accomplishment without communicating your results to the site.

People self-study text books without sending in their solutions to the publisher.

That's true. I am most interested in testing if my code works though. I don't see a 'cheat' option that gives you the correct answer I could check against.

I do see that the engine is open source though. I'll look into contributing: https://github.com/project-lovelace

Really cool. Sure the exercises are simple but a little reminder of some science concepts it's always nice.

Yeah haha they're definitely simple if you have almost any education in math or science.

I guess we started simple so that the barrier to entry is low, but we should have some tougher and more interesting problems soon!

What do you use for the interpretation of so many languages? Did you just build a bunch of sandboxed vms?

Ah do we run all user-submitted code in Docker containers. The "engine" that runs the code is written in Python and we do different things for different languages.

For running Javascript and Julia, it goes something like Python objects -> JSON -> read JSON in Javascript/Julia -> run code -> output JSON -> read user output from JSON in Python.

For C, we can call C functions directly from Python with some code for dealing with different types.

Not sure if this is the best approach (it's not super fast) but we've been learning as we go. We might be due for a refactor in case the next language we want to support doesn't fit into this pattern. I'm personally excited to learn Rust and maybe add support for it.

PS: Our stack is on GitHub in case anyone is interested in having a look: https://github.com/project-lovelace

From a quick glance it looked quite worrying, many red flags. I didn't look too carefully so some of this might be wrong or I missed where it's done.

* Results from the untrusted part inside container are returned using pickle. Which can be used to achieve arbitrary code execution outside container.

* no time limiting

* no memory limiting

* Untrusted code is run as root in the container which by default is same user as root outside container. From what I understand it isn't as bad as it was in earlier docker versions but still not great.

* untrusted code is run in the same process as semitrusted run_lang code, which means that the untrusted code with little bit of effort can manipulate reported execution time and memory usage

* for some languages correct_output is copied into the untrusted execution environment which means that solution could potentially just read the correct answers instead of calculating themselves

* none of the default capabilities are dropped which is probably more than what solution needs

* solution can freely create new files

Thank you so much for taking a look and letting us know!

Definitely not surprised that there are many security vulnerabilities...

I'm a grad student in computational science working on this as a hobby so building and securing websites is not something I know much about.

But now that someone is actually using it, I will take security more seriously.

Once I have some time I'll open a GitHub issue and compile a list of the security vulnerabilities you listed and will learn how to fix them.

This should be a good learning opportunity!

This should be a good learning opportunity!

That's a good attitude to have but people are probably going to take over your host[s], vandalize your site and run up your bills long before you get a chance to do all the necessary learning. I don't think your current approach is actually all that easy to secure.

I'm open to suggestions and advice if you have any.

This website is a free open-source side project and not business critical.

I don't have anything particularly concrete but I'd say find an open source implementation of something similar that has had a track record of running without too much incident and carefully copy its implementation, design and configuration.

My suggestions are:

Disable ability to make submissions until you have more solid plan

Decide what is your goal. Do you want to make a judge system, do you want create tasks or do you want a platform with specific kind of tasks.

Get in touch with people involved in ICPC an IOI contests in your country. Even if you are not interested in those kind of algorithm tasks, there will be some people who are familiar with similar existing systems and could point you in the right direction.

Assuming your primary goal isn't to make a judge system itself, some other options are: * Evaluate the existing online judge systems. There are some open source ones like DOMjudge(https://www.domjudge.org/), CMS(https://cms-dev.github.io/index.html) and others . Consider if you reuse or extend them to suite your desired format. In the worst case maybe just the execution part can be reused. At least learn from their experience and mistakes creating and maintaining such systems.

* Many programming languages now have online REPL environments. Some of them open source. This is one more source of projects that provide sandboxed execution.

* If you have some budget, there are platforms that provide sandboxed exection as service oriented at your exact use case. Some examples are Sphere Engine https://sphere-engine.com/enterprise used by Sphere online judge and Kattis .

There a lot more different platforms with different style of programming tasks than what you listed in your FAQ. Some of looking for problem setters. Maybe one of them fits your type of tasks more. Or it can be a one off contest with slightly unusual problem set. Or maybe it can be a separate category on their system and you can advertise this category on your website.

Thanks for the suggestion. Thread is too deep to reply to your actual message, but I will look around to see how other "online judge" software run arbitrary code securely.

There's probably some low hanging fruit in configuring Docker properly.

How do you check for malicious code, or something simple as "while True"?

There should be a limit on how long the Docker container can run code for, but it might be unnecessarily long right now.

I'm not a web developer by trade or anything so I'll have to learn how to secure the Docker container from malicious code. Hopefully Docker provides some amount of protection for now...

For today it's going to be old school htop + F9 haha.

Great site, lot of interesting problems.

Any chance of adding Rust to the list of supported languages?

In the Python templates, what’s with the variable “initialisations” —- e.g. t = 0 in the light-speed one? I’ve seen similar stuff in my eldest’s computing homework: is it an accepted Python idiom that I’ve missed somehow?

It looks like they've made the minimum amount of code that will execute (but not pass the tests). By using a variable instead of just hardcoding 0 into the return they give you a specific thing to assign to and as long as you leave that return t bit alone at the end your code will work.

Though, in that case, the solution is so trivial that t is completely unnecessary.

Yeah the other two replies explain why we used code stubs that would at least run but not pass.

Don't think it's an idiom (at least not one that I've seen).

It's definitely not the nicest code, especially for simpler problems that are really one-liners but we figured lots of people would just click "submit" on just the code stubs.

I presume it is to prevent a NameError if you run the template without adding any code.

Wow. I really like this!

Will begin solving all of them.

And I would like this to exists for a long time and I want it to be around when I teach programming to my little cousins, nephews and nieces and my future generation.

Add an option to Donate. Would love to do so.

They're nice and I'd like to see some more advanced ones.

But, why are the programs in Python instead of Ada, if it's Project Lovelace? For Python, maybe it could be Project Monty. Heh.

Off-topic: How you english speakers pronounce 'Ada'? Like [a]ffirmative or {a}pex?

'[A]da Lovelace' sounds so nice and soothing to me. It's a really beautiful name. However, just 'Ada' doesn't do anything for me, but 'Julia' does the trick there. A programmer named Ada Lovelace and a programming language named Julia... those things make for really comforting echos in my mind, I don't know why. Like coming home chilled from winter's rainfall and bathing the brain in warm vanilla sauce.

I've always heard Ada pronounced like in Apex. I like the language and find many of the complaints about it to be misplaced. I haven't tried Julia but I think its application area is completely different. I would say Ada isn't a great choice for this Lovelace project. Maybe the project should have been called Robinson instead of Lovelace, after the mathematician Julia Robinson (the R in the MRDP theorem, among other things). Then the examples could have been programmed in Julia. Or maybe even in R ;-).

Love the little explanations on the left!

I've used many of these same problems as small assignments when teaching programming to novices.

However all my assignments look much uglier. And looks do matter.

This looks awesome! I might try to incorporate this as an extra resource in an intro (Julia) class in the future.

That sounds awesome! Definitely let us know if we can help.

As a curious polyglot, this is great.

That's cool, but I'd love if you'd add Java to the programming languages.

Java is definitely on the list of languages to support soon!

I'm also thinking of how we can add a "manual submission mode" that lets you use any language that you run locally.

Awesome website! Although it often loads very slowly for me.

Thank you and sorry about the slow load time.

We never expected this much traffic and everything is hosted on a tiny DigitalOcean server including the code runner haha. If you visit a bit later it should be much faster.

I can think of some ways to speed things up which I will try.

It looks cool. Thanks! I've started solving problem in Julia. Are there 27 problem in total?

Also, I can not seem to submit solution to problem 'Compound interest'. I kept getting the following error, '...docker container is nonzero. Returning falcon HTTP 400.'. Sent you an email with the details.

Nice to see another Julia user! Yup right now we only have 27 problems but there will hopefully be many more in the future. Some people might even contribute some new problems.

This is great

What happens when you submit code?

The code gets uploaded to the server which sends it to an "engine" sitting in a Docker container. The engine generates test cases and send them with the code to another Docker container where the code is run. Then the output from your code is sent back to the engine which checks to see how many test cases you got correct before sending all the information back to your browser.

You can check out the engine code on GitHub if you're interested in the details: https://github.com/project-lovelace/lovelace-engine

Well done, thank you!

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