Methods of Proof — Diagonalization

, 10 min read

Very clear presentation on the uncountability of the real numbers, and the halting problem. Further keywords: Cantor, natural numbers, real numbers, diagonalization, bijection, Turing halting problem, proof by contradiction. -- -- -- Quote -- -- -- A while back we featured a post about why learning…

Photograph from Space

, 1 min read

Awesome picture. Also see Photographs from Space by Karen L. Nyberg.

Commuting to Work with an E-Bike

, 3 min read

My current workplace in Frankfurt is 20 km from my home. In the past years I used the train to go there. Unfortunately the train became more and more unreliable. Sometimes the train had lots of delays, sometimes the train just didn't arrive, sometimes the train was heavily crowded, often the…

Hard-Disk and SSD Speed Comparisons

, 1 min read

I bought a new Mushkin SSD with 60 GB. These are the results with gnome-disk-utility. These are the benchmarks for the ADATA with 128 GB. Just for the records another speed test for a classical Seagate 1 TB hard disk drive, old but venerable. See also Hard-Disk and USB Drive Speed Comparisons.

Installing OxygenOS 1.0 on the OnePlus One Smartphone

, 1 min read

Some notes and sketches to install OxygenOS on the OnePlus One, plus some remarks on my experiences. Download twrp. Download OxygenOS from here. Unzip the file and check MD5 of oxygen_1.0.0_flashable.zip with MD5 from web-page. $ cat oxygen_1.0.0_flashable.md5 2d79312774c44d2fa2bf5bb0c877d1b7 …

Speeding-Up Software Builds: Parallelizing Make and Compiler Cache

, 5 min read

1. Problem statement Compiling source code with a compiler usually employs the make command which keeps track of dependencies. Additionally GNU make can parallelize your build using the j-parameter. Often you also want a so called clean build, i.e., compile all source code files, just in case make…

Statistics of this Blog: Crossed 20.000 Views

, 1 min read

This blog was viewed more than 20.000 times. As in this post, here are the numbers: The averages per day are: The development of visits is as below: Top posts (all time) are: Most visits come from US and Germany by a wide margin:

Classical editor in WordPress.com

, 1 min read

The new editor in WordPress.com is quite annoying. It is annoying because: list of categories do not show up edit area is smaller "copy a post" is missing "format" menu is now a drop-down Unfortunately there is no option to switch back and forth between the annoying and the…

Four Free Invites for the OnePlus One, #5

, 1 min read

I have four free invites to purchase a OnePlus One smartphone. Below are the codes: GLU4-W66Y-VALB-PEPS GLZK-QIZH-3GAL-QQYQ GLQ5-74SJ-EDCA-GH1K GLRW-XU8U-8MSB-GQ28 They expire within one day.

Two Free Invites for the OnePlus One, #4

, 1 min read

Two more invites: GL05-1RXC-BCFK-C3VN GLCF-1RUJ-ODEW-1YZW These are now expired.

Two Free Invites for the OnePlus One, #3

, 1 min read

I have again two free invites to purchase a OnePlus One smartphone. Below are the codes: GLFB-GQM2-ZDHX-2XJM GLQW-0J5G-URN3-ZPIC The last two invites were just claimed, and were not actually used. This is really a waste of these invites, as there are a lot of people who really would like to…

Malcolm Gladwell on the financial crisis

, 2 min read

Yet another excellent speech from Malcolm Gladwell given at High Point University, see highpoint.edu. This time on Financial crisis of 2007–08 Battle of Chancellorsville between General Lee and Joe Hooker during the American Civil War in 1863 Overconfidence and miscalibration, results from…

Malcolm Gladwell on the importance of stubbornness

, 1 min read

A very interesting speech of Malcolm Gladwell on stubbornness in below YouTube video. Dead link. Video is here: Conference: Genius in 2012 He makes references to Linear B, i.e., historic greek symbols Michael Ventris, deciphering Linear B Andrew Wiles and his proof for Fermat's Last Theorem, no…

Importing Calendar Data to Google-Calendar

, 3 min read

Importing calendar data to Google is still troublesome for a number of reasons. What seems to work goes like this: Force-stop calendar app in your Android phone Clear all calendar data in your Android phone Shut down your Android phone Log-off from all other Google accounts Shut down your browser…

Two Free Invites for the OnePlus One, #2

, 1 min read

I have two free invites for the OnePlus One. Below are the links: GLYP-ATVO-YQ8K-D969 GLGQ-A0LM-I7RL-EKGB Please do not click on the links if you do not want to actually buy the phone, because the invites are then reserved and cannot be used by others. For a review of the phone see Review of the…

On Differential Forms

, 7 min read

Abstract. This article will give a very simple definition of $k$-forms or differential forms. It just requires basic knowledge about matrices and determinants. Furthermore a very simple proof will be given for the proposition that the double outer differentiation of $k$-forms vanishes. MSC 2010:…

Testing file-size limits

, 1 min read

For testing purposes you may want to provoke a file-size error. Here are the steps. Open a new bash/xterm. Set a file-size limit with ulimit, then write a file with dd. ulimit -f 1 dd bs=1 iflag=count_bytes count=5000 if=/dev/zero of=yourFile The resulting error is File size limit exceeded (core…

Average daily commuting time in Europe and the U.S.

, 1 min read

Below chart is taken from Stress That Doesn't Pay: The Commuting Paradox, August 2004, page 30. The data is per 2000/2001. The above document links these numbers with reported satisfaction with life -- longer commuting times means less happiness. Numbers change over time. Five year later the U.S.…

Using GnuPG for encryption and decryption

, 1 min read

On Ubuntu install with: apt-get install gnupg First generate private and public key: gpg --gen-key Generating this key can take some time, because it needs enough randomness. Store your public key in a file: gpg -a --export Although it is not necessary to store this public key, you usually will…

WordPress.com News and Numbers: Year 2014 in Review

, 1 min read

Im(Press)ive! Your Year in Review published some usage statistics for the year 2014, which are quite astonishing: 18,300,771 new blogs 555,782,547 new posts 24.5 TB/h (Terabyte per hour) Compare this with statistics from year 2013: 13,704,819 new blogs 489,281,136 new posts 667,675,929…