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kneth

293 karma · joined June 13, 2014

Chemist by education, geek by Nature [ my public key: https://keybase.io/kneth; my proof: https://keybase.io/kneth/sigs/GLbZtg2dN3w1hP-K1iIJqVXhtHFDboE2pyAaY_L4YrM ]
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kneth··on The CrateDB MCP Server
CrateDB (a distributed database for real-time analytics) is introducing its MCP server
kneth··on US quits Paris climate pact
Well, China has more than four times as many citizens.
kneth··on When memmove() Fails
The exception is related to emulating NEON instructions. So we are talking about very low-level exceptions (or signal handling) - at kernel/C library level.

I am not sure if this exception is the cause. And even if you could examine the assembler code, you will not be able to fix it: the affected devices have reach end-of-life years ago, and vendors will not fix the bug :-( The only chance for a fix is that app developers implement a workaround.

kneth··on When memmove() Fails
As the author of the article, I might be able to clarify a bit ;-). It is not absolutely clear to me what the bug is. It only appears on a few devices so it is not a trivial bug. It seems to be triggered by certain sizes and probably how the block is placed in memory. To answer your question: yes, the return value of memmove seems to be wrong in some cases. ChengYi He's analysis indicates that an ARM/Neon instruction is skipped which could explain the miscalculation. Why it skips the instruction (more precisely, why PC is not incremented correctly after returning from an exception) isn't clear to me or ChengYi He.
kneth··on Show HN: Realm (YC S11), a mobile database
I'm Kenneth at Realm. As realm databases are files on the phone's file system, you can use the common classes for manipulating them. To do a backup, the NSFileManager class might be useful (the copyItemAtURL method might be what you're looking for). See https://developer.apple.com/library/mac/documentation/Cocoa/... for details.
kneth··on Advice to a Beginning Graduate Student
My best advice to graduate students: enjoy!

If you're lucky, you have an advisor that teaches you much more than science and research. My advisor taught a lot about how to work in a political environment (yeah, universities are highly political environments).

If you are very lucky, you have an advisor that asks you to teach. By teaching undergraduate student, you learn all the small details of your scientific area. I was lecturing in physical chemistry as a graduate student - and even supervising undergraduates - and after a couple of years I knew all the fundamentals of physical chemistry by heart. That knowledge helped me through writing my thesis.

kneth··on Which programming language is used to express the most anger?
Surprising that the numbers are so low. It is frustrating to program as the devil hides in the details.
kneth··on Unix Tricks
Now and then I reread a chapter of "Classic Shell Scripting" (http://shop.oreilly.com/product/9780596005955.do) - probably the best book on shell script I know.
kneth··on Matlab alternative for math & science students
GNU Octave (http://www.gnu.org/software/octave/) is a great open source alternative to Matlab. I can only recommend the book "GNU Octave Beginner's Guide" (http://www.packtpub.com/gnu-octave-beginners-guide/book).
kneth··on SSH Tricks
Often (non-IT) companies' firewalls do not allow anything but HTTP and HTTPS traffic and you have to go through proxies. That implies that you cannot get to the outside using SSH. In my days as a freelance consultant, I used Corkscrew (http://www.agroman.net/corkscrew/) to get SSH access.
kneth··on 15 Little-Known Unix Commands
On OS X, I use "open" all the time. And often I use "bc" to do a quick calculation.
kneth··on The Art of Computer Programming: Random Numbers
If you're interested in Monte Carlo techniques for statistical physics, I'll recommend Kurt Binder's "Monto Carlo Simulation in Statistical Physics" (http://www.springer.com/physics/theoretical%2C+mathematical+...).
kneth··on Why Kids Care More About Achievement Than Helping Others
If you read the law for Danish public school system ("Folkeskole"; http://www.uvm.dk/Service/Publikationer/Publikationer/Folkes...), you find that one of the goals is to "contribute to the understanding of the interactions between people", and intellectual freedom and democracy are important concepts.

Reality might be different from the law, of course. Listening to my children (10 and 13 years old) and their friends, I find that they in general try hard to understand other children and wish to play/work as a group.

kneth··on Feenbox, RSS reader on your email
As an old-school UNIX user, I recommend feed2imap -(http://home.gna.org/feed2imap/) which does the same thing.
kneth··on Math for seven-year-olds
I introduced graph theory to my son when he was about 8 or 9 years old. By Nature, he's a networker (like to connect to people) so "friends of a friend" was very intuitive to him.

I have also tried to introduce the concepts to teenagers. In Denmark, we have an annual, national science weeks in primary and secondary schools. I have given http://www.slideshare.net/geisshirt/naturvidenskabsfestival-... as a talk/lecture at 4-5 schools and most 13-15 years old children get the ideas quickly - Facebook and other social medias are a big help :-)