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Ask HN: What's the hardest problem you've ever solved?

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Re: Ask HN: What's the hardest problem you've ever solved?

#81

Post by kephra »

I solved many challenging problems, e.g. I wrote a parser generator, that can generate itself, I wrote an UN/EDIFACT parser that was parsing the human readable UN standard to create a parser for a semantic translation. My Y2K PTFs run on every MVS and OS/360 system. I did a lot of machine learning in the last 10 years, e.g. optimizing maintenance of Siemens power plant turbines or quality control for injection molding machines.

But ... I'm taking the biggest challenge right now. I'm coding my Onyx database client idea for 3rd time. The hardest problem was to start o3db. I failed badly with Onyx 20 years ago by burnout holding over half a million lines of C++ in flow together with nearly 10k lines of my own 4gl, during the 3rd customer installation of Onyx. I was very shy of coding UI/UX afterwards, escaped deep into server stuff, machine learning - escaped as far away from user as possible.

So, my biggest challenge was to start Onyx again: A user facing UI/UX for common business database applications with its own fourth generation language. I've decided for Scheme as an intermediate language this time, and the prototype running well. I now have a non recursive Scheme interpreter and GUI running in browser, able to process the meta tables defining an application. Its still a long road to my vision. But to start a project again, I failed with a burnout 20 years ago, and to code it with actual technology, was the biggest personal challenge.

/join #o3db on freenode, if interested in a startup to create common business database clients for the web.

Re: Ask HN: What's the hardest problem you've ever solved?

#82

Post by Libbum »

Difficult to say this problem is solved yet - the jury is still out, but I've done a good deal of work on identifying what the mechanism of a defect in superconducting phase qubits may be.

TL;DR: Two level system defects are a 20 year old unidentified noise source that can be described by an oxygen spatially delocalising in an amorphous portion of the underlying circuit.

See http://dx.doi.org/10.1103/PhysRevLett.110.077002 and http://dx.doi.org/10.1088/1367-2630/17/2/023017.

Re: Ask HN: What's the hardest problem you've ever solved?

#84

Post by JensRantil »

danudey wrote: post #76

Setting up an IPSec VPN from a Linux server to Amazon VPC and running data over it. There was a host of documentation on how to do similar things with the appropriate tools, but as always, it was document A with 40% of the puzzle, document B with a non-overlapping 30% of the puzzle, and document C with an overlapping 40% of the puzzle… at which point I realized that all three documents were using different approaches…

This is funny because I am basically about to try and diagnose a _very_ similar issue with a VPN tunnel between a Cisco ASA and AWS. I'm also seeing SYN/ACK being occasionally dropped and TCP connection states ending up in WAIT state.

Re: Ask HN: What's the hardest problem you've ever solved?

#85

Post by JensRantil »

I used to work at a VOIP provider where users started reporting choppy audio. After a week or two we nailed it down to customers that had "call recording" feature enabled. Essentially their calls were being recorded and streamed to an audio file to be accessed later through a web interface. After yet another week of investigations we noticed that disk IO was fairly high on machines that had big customers with call recording enabled for all their endpoints. We drilled the IO issues down to the WAV file format that has a header that needs to be updated for every write to accomodate for the updated length of the recording. This required a lot of disk seeks on spinning disks and unfortunately file flushing could not be disabled.. Switching to a RAW audio format that we post-processed after the call resolved the issue.

Re: Ask HN: What's the hardest problem you've ever solved?

#88

Post by Tiksi »

TeMPOraL wrote: post #69
_chendo_ wrote: post #39

Going to list a few interesting problems that were easy to solve but the identification of the issue was hard. * A test suite we wrote for a client's project before a massive refactor was stalling randomly, but would continue when you tried to diagnose the problem. Turns out their user creation code used /dev/random, and the system was running out of entropy and so the code was blocking. Moving the mouse or typing on…

> Turns out their user creation code used /dev/random, and the system was running out of entropy and so the code was blocking. Moving the mouse or typing on the keyboard would add entropy, thus cause the tests to resume. Funny how this goes completely against the typical operant conditioning a user undergoes when working with computers. Usually if your software hangs up, you want to touch nothing and let it finish. B…

It seems perfectly in line with what I generally see. A hang up usually results in some desperately mashed combination of Esc, Space, and Enter, then clicking on absolutely everything, and finally mashing ctrl-alt-del in the hopes of something happening. The let it do its thing and wait crowd has always been on the higher end of the technical knowledge spectrum.

Re: Ask HN: What's the hardest problem you've ever solved?

#89

Post by abrookewood »

odabaxok wrote: post #58

Debugging can be hard sometimes, too. Here is a Quora topic about it: http://www.quora.com/Whats-the-hardest-bug-youve-debugged My favourite answers: Crash Bandicoot: http://www.quora.com/Whats-the-hardest-bug-youve-debugged/an... Flash Player: http://www.quora.com/Whats-the-hardest-bug-youve-debugged/an... 500-miles email: http://www.ibiblio.org/harris/500milemail.html

500-miles email is a fantastic read - thoroughly recommended.
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