, 4 min read
I was recently asked about my opinion regarding agile software development. I think the core problem is not agile or extreme programming, or object-oriented or structured. I think this simply misses the point. Below are the key ingredients to succeed in software development when it comes to…
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Good summary of some current JavaScript grid solutions. See also JavaScript Open-Source Spreadsheets and Data Grids.
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Architecture per core: At the chip level, 8 cores per CPU: Registers per core: Unfortunately I didn't find opcode clock cycles on AMD's website. AMD's website seems to be almost unmaintained, i.e., lots of dead links. Below are some clock cycles gathered through experiment by Agner Fog. I took…
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The world largest economy shut down its most prestigious space center agency. Wikipedia provides some background information here: government shutdown. Regarding NASA it says: NASA will furlough 98% of its staff, leaving fewer than 600 out of more than 18,000 employees on the job. NASA will…
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Google CFO, Patrick Pichette, on the evolution of computing power storage capacity network bandwith He shows the following remarkable slide on the disparity of the latter to the former. It was this disparity which apparently led Google to enter the broadband market with its own…
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Most common usage of rsync is rsync -anv ./ user@remote:/dir/ But when the timestamps of the files on source and target vary wildly it is better to use: rsync -crntlv ./ user@remote:/dir/ The option -c stands for checksum. The option -n is used to not overwrite anything (dry run). Drop -n to…
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Amazing photographs from astronaut and engineer Karen L. Nyberg on Twitter during ISS-Expeditionen 36/37: The astronauts and engineers in space have internet: NASA Extends the World Wide Web Out Into Space. BTW, Karen L. Nyberg also posted a photo of a dinosaur in space.
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Below journals, loosely related to topics in Numerical Analysis, offer unencumbered full text: Electronic Transactions on Numerical Analysis Applied Mathematics E-Notes (no longer active) The Electronic Journal of Linear Algebra arXiv Unfortunately, Numerische Mathematik, BIT, SIAM Journal on…
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I have now done it a couple of times, but always have to look it up. Here are the steps to re-install Grub from a live Ubuntu CD, when you have Windows and Linux on your hard disk. You must be root, or run these commands with sudo. Change /dev/sdaXY accordingly. mount /dev/sda2 /mnt mount…
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Below I copy some paragraphs from a recent article in Polymath 8 – a Success! | Combinatorics and more by Gil Kalai on Zhang’s breakthrough regarding prime numbers: Twin primes are two primes $p$ and $p+2$. The ancient twin prime conjecture asserts that there are infinitely many twin primes.…
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Except notably Russia and Africa this blog has been visited by quite a number of countries. I am surprised. Also see Statistics of this Blog: Top Views by Country.
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Very interesting talk on the scaling challenge at WordPress.com given by Barry Abrahamson, CTO of WordPress. Some key points: 500 million database tables 3 data centers in USA 400.000 shards moved per day storage on SSD ~10% of total infrastructure costs are related to backups ~500 GB / shard 50…
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Below table is from work-with-us (data as of 22-Sep-2013): One of these things is not like the other. Company NameMonthly Uniques…
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Georg Hager's Blog posted an illustrative article on icc versus g++ performance w.r.t. OpenMP. Dr. Georg Hager is one of the authors of Introduction to High Performance Computing for Scientists and Engineers. Measurement of double precision, dimension(N) :: a,b,c,d ! initialization etc. omitted s =…
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JpGraph is a library of PHP code to draw a variety of graphs: line+bar+pie charts radar+polar+contour graphs bar+QR codes Gantt charts a couple of other chart types Here are two examples: JpGraph is a free product by Asial if used in a non-commercial context. Installation is quite easy on…
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Inspired by a discussion with my son regarding movement of a point-charge between two other charges I revisited the definition of the line integral. Wikipedia offers an excellent visualization of the definition of the line integral for a vector field. See animated graphic below: This is something…
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Just read on Torricelli's trumpet in Wikipedia. This states that there is a body having infinite surface but finite volume! That sounds contradictory at first. Function in question is $$ y = 1 / x $$ from $x=1$ to $a$. Volume is $$ V = \pi \int_1^a \left({1\over x^2}\right)\,dx =…
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Brian Koberlein wrote a very good introductory article on curvature of space and time in the vicinity of gravity: see The Attraction of Curves – Brian Koberlein.
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Last year I used a drop-in replacement for the ordinary Linux sort command called nsort from Ordinal Technology. Ordinal's nsort is free but not open-source. One thing is clear, however, it is very fast. nsort was written by Chris Nyberg. The motivation for looking for a faster sort was as follows.…
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Below picture is from Read Throughput Average (dead link) in Tom's Hardware.