I am hoping to get people back into hobbies that they have lost interest in or have fallen out of the loop.
I have build a VERY basic landing page but I am struggling to get time to spend on it.
Ask HN: What interesting problems are you working on?
411–420 of 709 posts
Re: Ask HN: What interesting problems are you working on?
#412How to find an accurate numerical
approximation to e, the base of the
natural logarithm? Last weekend stumbled
onto a shockingly easy and effective
way!
Google query
"base of the natural logarithm e"
reports
e = 2.718281828459
that is, 13 digits.
The calculator with Windows 10 reports
e = 2.7182818284590452353602874713527
that is 32 decimal digits.
Last weekend found
e = 2.71828182845904523536028747135266250
that is, 36 decimal digits.
The math and code are below and could just as easily get e to, say, 500 decimal digits!
How'd that happen?
Last weekend worked on some short but relatively careful notes to get a nephew of 9 started on calculus, and part of that was Taylor series in just two pages with large fonts!
The code and the core of the Taylor series derivation are below.
In TeX, Taylor series is
f(x) = \sum_{i=0}^n {(x - x_0)^i \over i!} f^{[i]}(x_0) + R_n(x_0)
with R_n(x_0) as the error term.
To derive the Taylor series, really just find the error term
R_n(x_0)
and for that just differentiate f(x) with respect to x_0 where then nearly all the terms cancel, simplify, integrate from x_0 to x, and apply the mean value theorem. That's all there is to it!
The results are, for some s between x_0 and x:
R_n(x_0) = (x - x_0) {(x-s)^n \over n!} f^{[n+1]}(s)
As above, the final output of the code:
e = 2.71828182845904523536028747135266250
From R_n(x_0) the error is less than
3 x 10^(-40)
The numerical output of the code is curious: Get a little over 1 decimal digit of accuracy for each term of the series! So the output shows two big triangles, one for the values of n! and one for the number of correct digits in the estimate of e.
A key to why this code is so simple and works so well, Kexx can do arithmetic with 1000 decimal digits of precision!
"Look, Ma, here's the code -- dirt simple":
macro_name = 'NATLOG'
out_file = macro_name || '.out'
'nomsg erase' out_file
Call msgg macro_name': Find natual logarithm base e'
numeric digits 1000
n = 35
sum = 1
factorial = 1
Do i = 1 To n
factorial = i * factorial
sum = sum + 1/factorial
Call msgg Format(i, 5) Format(factorial, 50) Format(sum, 2, 35)
End
error = 3 / factorial
Call msgg macro_name': The error is Re: Ask HN: What interesting problems are you working on?
#413I've been meaning to improve "news" for a number of years now, with limited success so far. The current news industry is broken beyond repair: all you get are bite-sized irrelevant factoids. A good news service would be: - Relevant to you and your interests... - ... but diverse enough to feed your intellectual curiosity - Delivered in a timely fashion: apart from once a year big events, most things can wait for a few…
Hey, just to give you some inspiration. There is a company in the Netherlands that tries to do what you set to do. It is called Blendle https://blendle.com/
The website is all in Dutch, but you can probably get the gist of it (I live in the NL but don't speak Dutch, but their mission is quite clear).
Re: Ask HN: What interesting problems are you working on?
#414We are working on how to match engineers with engineering teams based on the work environment and team values/culture. I've had too many friends and family members end up at companies that were not a match and watched the massive stress pile up. I want to help people find the right team/culture for them.
Sounds interesting, I always like to see good ideas in the hiring space. How do you differ from something like https://www.keyvalues.com/
Thanks! I love what Lynne is doing!
We differ in a lot of ways, but the biggest is that we are trying to profile the actual eng team and how they work / what they value. And, then match you with teams that are a good fit + high satisfaction in key areas.
For example, say you are motivated by big tech challenges, we would match you with teams that are motivated by similar and report satisfaction in that area from their current eng team.
Re: Ask HN: What interesting problems are you working on?
#415An acoustic system for poor-visibility tunnel evacuation assistance using psychoacoustic effects. Massively distributed, self calibrating, microsecond scale synchronized system with a bunch of interesting problems in software, electronics, acoustics and mechanical engineering.
Re: Ask HN: What interesting problems are you working on?
#416I'm helping build a mathematics tutoring system. Compared to classic math learning, we are trying to mimic the strength of a real tutor. Which is, identifying the lack of math skills and teaching those. From our experience the biggest issue students have is, they can't solve an issue because they didn't understand a concept they have already "learned" in the past. It's simple, yet powerful.
Is it on github?
Re: Ask HN: What interesting problems are you working on?
#417Earlier quoted context omitted.
I'm also in the planning stages of re-writing ~1M lines of C doing hardware control for a telecoms system. It's going to be replaced with Elixir (basically Erlang) because it's the perfect fit (which is unsurprising given its a telecom system). My prediction is that it will be 10-20k lines of code when I'm done because there's so much obsolete cruft to remove. Plus ~1k of C as a shim layer to allow an incremental tra…
Nice, glad to know there's other brave souls that choose the Big Rewrite path, despite the latent idea in our industry that every one of those projects are meant to fail.
My approach is that there are a few things that the default answer for should be "no" and then you have to justify (maybe just to yourself) why they're appropriate in this case. Macro Fu in C, template meta-programming in C++ and rewriting from scratch are all examples of these.
In this case I am avoiding the 'throw it all away and start from scratch' approach. It would be infeasible for the intervening period. I am putting together an approach that would get us there in a year or so, but we can lop off smaller chunks to rewrite (the existing architecture is a series of daemons, which helps us there).
Re: Ask HN: What interesting problems are you working on?
#418I've had an idea for some time now to create a website that would act as a better codereview.stackexchange.com. It would incorporate some of the features of the GitHub Pull Request system like inline commenting and reactions. I arrived at this idea from two directions. The first direction is that I sometimes try to code review some of the questions over at CodeReview SE, and the whole thing feels unergonomic. I disli…
I thought about the same thing! I think having your code reviewed is one of the fastest ways to improve and at the same time, it's currently very hard to have it done. I really dislike CodeReview SE for many reasons though, I don't think this Q&A format is suitable for doing CRs
Hey, what kind of things do you dislike about the CodeReview SE and what would you like to see in an improved code review system?
Re: Ask HN: What interesting problems are you working on?
#419An acoustic system for poor-visibility tunnel evacuation assistance using psychoacoustic effects. Massively distributed, self calibrating, microsecond scale synchronized system with a bunch of interesting problems in software, electronics, acoustics and mechanical engineering.
Could you go into detail? Or explain what that means? It sounds interesting, but none of the words seem connected.
Re: Ask HN: What interesting problems are you working on?
#420Earlier quoted context omitted.
Yeah if you drill into how the Tesla grid storage solutions make money, it’s not just about the storage capacity but also about being able to respond to demand or frequency issues extremely quickly, which LiIon batteries are very good at. There’s a lot of money available to the fastest dispatcher.
A lot of money seems excessive, at least in Europe. The flexibility market profitability depends a lot on the national market it plays in, as for instance the prices are quite low in Germany/north Europe, but very high in Australia. Rather than a way of making money, I like to think about flexibility and fast dispatching as an enabler for way more renewables to come online, and that is crucial for the human race righ…
Makes sense -- the grid storage system I read about was indeed the one they built for the Australian wind farm.
I think there's a big gap for both types of storage - fast dispatching for intraday demand variations, replacing gas peakers, and more static storage as in the OP for multi-day gaps in renewable production such as periods of high pressure during winter when wind speeds and irradiance are both very low.
Can't wait to see how this market develops.