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Ask Slashdot: How Would You Build a Home Network To Fully Utilize Google Fiber?

Terje Mathisen Permanent conduits are the only way to go! (279 comments)

Here in Norway all electrical cables are installed inside plastic tubing, so you can pull out/replace them if you need to, with no need to tear down any walls. (BTW, we also do the same for water pipes: They are always installed as pipes-in-pipes, with a central drain point for the external pipes: This way any leak will be contained and you can fix it by pulling out the broken (usually due to freezing in winter) pipe and replace it.)

When we built a new home a few years ago I specified that the electricians should put in spare conduits between the main breaker room and every other room in the house, except bathrooms, this way I could pull whatever cable I would need.

PS. The sad part of the story is that the installation company had never done anything like this in a residential building before and they messed up badly, omitting the spare conduits to important locations like the living room/entertainment center. They ended up giving me a substantial rebate but I'm still a bit pissed off. :-(

about two weeks ago

The Frustrations of Supporting Users In Remote Offices

Terje Mathisen Re:BT, DT... (129 comments)

You are right, if it had been a pure Dos problem those would have worked, this probably means that the partition table was the victim, but I obviously don't remember all the details now. :-(

about a month and a half ago

The Frustrations of Supporting Users In Remote Offices

Terje Mathisen BT, DT... (129 comments)

Many, many years ago (1986 or so?) we had a branch oil exploration office in Iran, surveying new oil fields close to the border with Iraq.

Getting any kind of computer gear in or or out of the country was "difficult", and the best possible data connection was an extremely expensive 256 kbit/s satellite line.

One day I was told to help, over a bad phone line, a guy down in Teheran whose PcDos computer had crashed:

I was able to figure out that his crash had modified/overwritten the Boot Block on his hard drive, but that he did have a bootable Dos diskette available, so I sat for about 45 minutes on the phone, talking him through the DEBUG commands needed to load the boot block and manually modify it back to how it should have been, then write it back.

It worked on the first attempt. :-)


about 1 month ago

Soccer Superstar Plays With Very Low Brain Activity

Terje Mathisen Mastery has to be (at least partly?) subconcious (160 comments)

When grading expertise on any given task/process, the top level ("Master") is usually defined to be when the person can not even explain how she is doing it, everything is automated to such a degree that "the solution was obvious".

Magnus Carlsen used to play even faster than he is doing these days, but he explains that this is not because to takes him longer to figure out the best possible moves, but because he has to take the time afterwards to do all the required calculations to confirm his instinctual choices.

He has also explained after some really complicated end games where he has kept on playing for small advantages, eventually turning "obvious draws" into wins, that "it was very easy, I just had to play the only possible move".

I believe the foot/leg motor skills of a Neymar is comparable to those of a world champion orienteer: The best orienteers can run cross-country, through rocks, stones, windfall & vegetation, while studying an incredibly detailed map in order to navigate, making it impossible to focus on the ground while looking at the map. This means that the actual broken field running must use a small amount of brain capacity, all the movements are fully automated.

I know that Petter Thoresen (former multiple world champion) once was told to do a training race in Germany while a champion Kenyan cross country runner would tail him to check his technique: Even while orienteering Petter could run fast enough that the x-c runner was dropped after less than a mile.


about 3 months ago

Laser Eye Surgery, Revisited 10 Years Later

Terje Mathisen Re:"poor night-time results": I do Night-Orienteri (550 comments)

Thank you!!!

This is exactly what I've been waiting for, even if this first version only supplies a single diopter of focal plane adjustment:

Since orienteering maps are _very_ detailed I normally require +2 or more bifocal glasses in order to see all the fine detail clearly.

There is also a potential problem with the size of the lens: The visual opening is smaller than a natural or fixed replacement lens so the problem with night vision would still be there.

OTOH, this also means that the research is ongoing, I'm hoping for even better options in a few years. :-)


about 3 months ago

Laser Eye Surgery, Revisited 10 Years Later

Terje Mathisen "poor night-time results": I do Night-Orientering! (550 comments)

I normally run around 75 orienteering competitions every year, 15-20 of them during late fall/winter/early spring when we have very little daylight here in Norway.

This means that those races are all at night, using a LED headlamp to read the map and to the see the ground in front of me. Since I got old enough for presbyopia I have been forced to use either bifocal glasses or a single contact lens: The glasses work OK under dry daytime conditions, but with any kind of moisture in the air they quickly become useless. The single contact means that I can only see the map with my right eye and the terrain only with the left, while distance perception suffers.

When I asked about lasik I was told that with my need for maximum night vision I would probably be very bothered by halos/diffraction spikes, the alternative is to do a multi-focal lens replacement surgery:

This uses a lens with two or three focal points, i.e. distance/reading. Most people can learn to disregard the out of focus image and only "see" the sharp version, but since more than half the light is lost night vision suffers significantly.

I'm still hoping they will be able to develop a real elastic replacement lens, i.e. something that allows me to regain the childhood capability to focus anywhere from the tip of my nose to infinity, in the meantime I'll try to make do without surgery.


about 2 months ago

Geographic Segregation By Education

Terje Mathisen Dual-income couples drive this! (230 comments)

At least here in Norway this trend probably started even earlier, but we have a significantly larger proportion of dual-income university-educated couples. (This trend is supported by our one-year parents leave with pay, where the parents have to share this time, and by public kindergartens when the children are a little older.)

I suspect that a strong driver for this big city concentration is the fact that most couples meet sometime during their university studies, and when this switched from being men getting their MSc's meeting the girls from the nursing schools, to being men & women at the same university, they would have really strong incentives to try to settle in a city with a big enough employer base that both would have multiple job alternatives.

I.e. my wife & I have lived in Oslo for almost 30 years now, we have always had lots of employment options, while my youngest brother and his wife live in a far smaller town:

In their area it has significantly harder to locate alternate (and interesting) employment when bad times hit the company one of them worked at.


about 3 months ago

Exploiting Wildcards On Linux/Unix

Terje Mathisen Re:Question... -- ? (215 comments)

The real bug here is the same as in SQL injection attacks: A failure to safely distinguish between program and data!

I.e. when doing chown usr:grp *.php, the wildcard globbing should escape any special letters, particularly including white space and wild card characters.

This is the same idea as when you use prepare(... ?,?) on any sql statement with replaceable parameters, then execute() with the relevant dynamic values.


about 4 months ago

Ask Slashdot: Where's the Most Unusual Place You've Written a Program From?

Terje Mathisen Special locations? Oh Yes! (310 comments)

10 meter below the sea surface, inside one of the legs of a semi-submersible drilling platform in the North Sea in winter (Dec 1981).

About 98% relative humidity, 10+ C, water dripping everywhere, including a pulsing spigot from the 10 cm long crack we were down there monitoring.

We had lowered a full lab worth of expensive HP gear into that environment and I did on-site programming (digital signal analysis) on an 8-bit HP-87 microcomputer.

The software worked and all the gear survived, even if we had to unpack it from the shipping boxes in order throw a rope around each unit and first lower them and then afterwards pull them back up the narrow manhole inspection ladders.

Later in the same decade I wrote what might be the ultimate executable ascii generator while on a skiing vacation in a mountain log cabin (no computers, just a notebook and a hex dump of all the x86 16-bit opcodes.

My version ran using only the 70+ chars that MIME specifies as not needing any form of encoding.

It used the minimum possible amount of self-modification in the bootstrap loader ( a single two-byte backwards branch).

It survived most common forms of reformatting, i.e. changing line terminators from CRLF to just LF (unix) or just CR (Mac), or merging all lines in a paragraph into one.


about 5 months ago

Ask Slashdot: What Inspired You To Start Hacking?

Terje Mathisen Not MIT but NTH (153 comments)

I started at NTH (currently called NTNU) in Trondheim (Norway) in 1977, so my first-year programming class was in Fortran 2, hand-punched on 80-column cards.

I can still recall my sense of wonder when I realized (during the second lab exercise or so) that "I can make this computer do anything I like!".

My first ever extra-curricular program used modulo 1e10 arithmetic on a 36/72 bit machine in order to calculate pi with as many digits as I could manage within the 60 cpu seconds which was my maximum allotment.

Since then I've done an awful lot of hacking, but almost exclusively in the old meaning of the term.

Currently I'm playing around with hardware/software codesign on the Mill computer architecture, writing fast & efficient fp emulation for machine models without full hw fpu.


about 5 months ago

Why Scientists Are Still Using FORTRAN in 2014

Terje Mathisen Re:Q: Why Are Scientists Still Using FORTRAN in 20 (634 comments)

Fortran has had "higher-order array operators" for _many_ years now (see FORTRAN 90), but even without this most Fortran code is written using simple iterative operations over arrays, with explicit multi-dimension indexing. This tends to make the auto-vectorizers job much simpler.

As the AC noted, Fortran has pretty much no aliasing issues at all, unless you go out of your way with COMMON blocks, this makes it far easier to optimize the code.


about 5 months ago

Ask Slashdot: What Tech Products Were Built To Last?

Terje Mathisen Fluke is indeed no fluke! (702 comments)

My Fluke multimeter which I got from my new boss the day I started my first job outside university back in 1984 (i.e. 30 years ago) is still working just as well as on the first day.

I have to replace the 9V battery every 5 (3-10?) years, but otherwise this little gem has survived everything, including several accidental drops, some from more than 2m height.

Really good stuff.

The portable Fluke digital oscilloscope (Scopemeterl 123) which I got 10+ years later is also working well, the only problem here is that it uses an old-style NiCd rechargeable battery which I've had to replace once. Fluke seems to be selling it still, under the 123/S name. :-)


about 6 months ago

Slashdot Asks: How Do You Pay Your Taxes?

Terje Mathisen Norway is similar... (386 comments)

For a large majority of Norwegian citizens the old nightmare of filling in the tax return has been reduced to a very simple scan:

Does the pre-filled tax return I got in the mail (or checked online at the government site using secure two-factor authentication) include everything it should, i.e. all income, bank statements, any funds/stock and/or debts? The answer is Yes for something like 70%+, in which case they can do nothing, or accept it via the online site or even using SMS.

My personal return can have some consulting fees on top of my normal salary, so I have to login and add an extra income item, then submit the updated return.

Total time spent is about an hour.


about 6 months ago

Ask Slashdot: Will Older Programmers Always Have a Harder Time Getting a Job?

Terje Mathisen Is 40 the "new old"? (379 comments)

I'm 56, should I be forced to retire?

Programming is still something I do more or less 7 days a week because I like it, not to get rich or just because I'm paid to do so. When I started out this was pretty much the only way you could get into programming, i.e. my (technical) university didn't even offer an IT degree when I started there.

I've been programming since the seventies, I have written MBs of source code in many languages, but of course I'm getting about a year older every year. :-)

The main difference between today and 25-30 years ago is probably that now I'll spend a bit more time up front thinking about the problem _before_ I sit down to write the code. I've taken part in 3 of the 4 Facebook Hacker Cups that have been held so far and I've noticed that I get into trouble in the later rounds when time pressure becomes critical, but I like to think that I'm still coming up with good solutions even if it takes me more than 30-40 minutes to do so.

The international competitions that I've won have been for the fastest possible code but with some weeks to deliver the solution.


about 7 months ago

DDoS Larger Than the Spamhaus Attack Strikes US and Europe

Terje Mathisen Update your NTP sw! (158 comments)

I've been a member of the NTP Hackers team for more than a decade, the mechanism that is being abused for these attacks is in fact a very useful debugging/monitoring facility:

You can ask an ntpd server about how many clients it has and how often each of them have been accessing the server. On old/stable ntpd versions this facility was accessed using a single pure UDP packet (ntpdc -c monlist), and in reply you got back information about up to 602 clients (the size of the monlist buffer), sent as a big burst of UPD packets.

Researchers have developed maps of the entire publicly accessible NTP networks using this facility, I have personally used it to map the status of our fairly big corporate network. I.e. it can be extremely useful!

A few years ago the development version of ntpd switched to a different protocol and method to query this information, using a nonce which meant that you can no longer spoof the source address: (ntpq -c mrulist). Since the mrulist buffer is configurable, I have setup my public ipv6 pool server ( [2001:16d8:ee97::1]) to keep monitoring info for the last 10K clients.

Today we recommend that you either upgrade to ntpd v2.4.7, or if you really cannot do this, insert a 'restrict default noquery' option in the ntp.conf configuration file. The 'noquery' indicates that clients can still use the server for regular time requests, but the monitoring facility is disabled.


about 8 months ago

Dead Reckoning For Your Car Eliminates GPS Dead Zones

Terje Mathisen This was required before the end of SA! (151 comments)

All car navigation systems pretty much required this when the GPS system was still hobbled by the ~100m uncertainty caused by Selective Availability. (Ended by Clinton in May 2000).

The implementation is actually quite trivial: One sensor on each front wheel gives you two revolution counters (odometers).

Distance traveled is proportional to the sum of the two counters, while the difference in counts is proportional to how much you have turned.

As long as you have GPS reception you can use that to calibrate the odometers, so that differences in tire type & pressure is automatically compensated for.

Using a barometer you can do the same for altitude, automatically compensating for changes in local air pressure.


about 8 months ago

Nobel Prize Winning Economist: Legalize Sale of Human Organs

Terje Mathisen Re:Read Larry Niven's stories about "organleggers" (518 comments)

Thanks for posting, I was going to mention Niven's entire ARM series as required reading for _anyone_ who want to debate the relative merits of various forms of organ donation/transfer.

I registered as a blood donor on my 18th birthday, my bone marrow profile has been in the data banks for a couple of decades (but with no harvest requests so far), and if I should ever suffer from a fatal accident my next of kins have all been informed that I would like as many of my organs to be reused as possible.


about 9 months ago

Coca-Cola Reserves a Massive Range of MAC Addresses

Terje Mathisen Minimal range, not massive! (371 comments)

MAC addresses consists of 48 bits, of which 24 is a vendor code and the other half some sort of serial number.

I.e. the smallest possible allocation of MAC addresses is a single vendor code, giving 2^24 or 16M unique addresses.

Sounds like an obvious starting point for a Coca-Cola MAC address in every vending machine.

about 10 months ago

Ask Slashdot: Do You Run a Copy-Cat Installation At Home?

Terje Mathisen I go to work to have fun. Don't you? (308 comments)

I've been spending many hours of my free time in front of a screen like now, close to every day since the day I got my first personal computer (an IBM PC clone back in 1982).

This was two years before I landed a job working on PCs (chief responsible for all hw/sw on IBM compatible PCs in Norway's largest corporation), when I understood that they wanted to pay me good money (50% more than I was currently making) for doing what I was already doing as a hobby I was very pleased indeed.

Since then I've written several tens of MBs of code (about 20+ MB before 1990), most of it in my free time even if I later could reuse many programs & algorithms in my daytime job. I have always had at least a couple of computers at home, currently I have just one big deskside tower and a bunch of laptops. They run Windows 7 & 8, as well as FreeBSD (my gateway/fw/ntp stratum 1/ipv6 gw box) and Linux.

I've been able to work on a lot of interesting projects (if you google my name you'll find a few), including game code, ntp, crypto, graphics, video/audio decoding, simulation and modeling.

Currently my main hobby project is to take raw LiDAR point clouds and use pattern recognition to try to generate vector base maps for orienteering, including shades of green and yellow to represent various degrees of runability and visibility.

When I was ~20 years younger I won or made it to the podium in several programming/optimization contests, these days I've taken part in 3 of the 4 Facebook Hacker Cups that's been held so far. I usually make it to the second main round but I'm not fast enough any longer to get into the top 100 who make it to the finals. The main part is that it is fun to figure out problems and come up with efficient algorithms!

They key message here is that even though I'm getting closer to retirement age, I have absolutely no plans to stop thinking/thinkering!

about 10 months ago

The Cybersecurity Industry Is Hiring, But Young People Aren't Interested

Terje Mathisen Bulls**t: 24% is a _lot_! (289 comments)

Please give me a big list of other occupations which more than 24% of a random sample of kids are interested in, then I'll allow you to claim that too few youngsters are interested in cybersecurity.


1 year,2 hours



SlashDot reference in QuestionableContent

Terje Mathisen Terje Mathisen writes  |  more than 6 years ago

Terje Mathisen (128806) writes "The very good online comic made a small story break today (comic #1023), in that Hannelore, the girl with Compulsive Cleaning Disorder is shown watching TV commercials for "Wikipedios" (soup cans containing pasta letters spelling out Wikipedia articles), and then in the last panel:

"Try SLASH-DOTZ! Tasty ice cream dots with a minty candy shell! They're +5:Delicious!""


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