, 4 min read
Ico Doornekamp on 20-Dec-2011 asked why a C version of a Lua program ran more slowly than the Lua program. The mentioned discrepancy cannot be reproduced, neither on an AMD FX-8120, nor an Intel i5-4250U processor. Generally a C version program is expected to be faster than a Lua program. Here is…
, 1 min read
Christian Terboven and Dirk Schmidl from IT Center RWTH Aachen presented a deck of slides on OpenMP: Introduction to OpenMP OpenMP Tasking In Depth OpenMP Recap OpenMP and Performance Advanced OpenMP Features Some very striking slides are reproduced here. Not directly related to OpenMP but…
, 8 min read
I recently read in Computers are fast! by Julia Evans about a comparison between fread() and mmap() suggesting that both calls deliver roughly the same performance. Unfortunately the codes mentioned there and referenced in bytesum.c for fread() and bytesum_mmap.c for mmap() do not really compare…
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This blog was viewed more than 30.000 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:
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See the fireworks Elmar Klausmeier's Weblog created by blogging on WordPress.com. Check out their 2015 annual report. Here is an excerpt: The concert hall at the Sydney Opera House holds 2,700 people. This blog was viewed about 14,000 times in 2015. If it were a concert at Sydney Opera House, it…
, 1 min read
Today I received an invite for the OnePlus X. The code is: GL71-90E4-75E1-DBA7. This invite is valid for 3 days.
, 1 min read
I got above error message in nginx. Stackoverflow post 413 Request Entity Too Large - File Upload Issue had all information to resolve the issue. The solution was written by User Arun. One has to edit /etc/nginx/nginx.conf and add in http{...} client_max_body_size 15900M ; and /etc/php/php.ini ;…
, 2 min read
Below is a short overview of small scale computers for use in embedded computing. Intel Galileo, single core Quark/Pentium, ca. 100 USD, <15 W Intel Edison, dual core Atom Silvermont, 500 MHz, ca. 100 USD, <1 W Raspberry Pi, single core ARM, 700 MHz, ca. 35 USD, ~1 W Arduino series, e.g.,…
, 2 min read
I had to detect Windows junctions (similar but not identical to symbolic links) in Python. On stackoverflow.com I read the following Python code given by a user named eryksun for handling them, as os.islink() does not work for junctions. The routines access Windows functions CreateFileW(),…
, 1 min read
Brian Koberlein mentioned that NASA provided photos from Apollo moon mission on Flickr.com. Below is one:
, 2 min read
Advertisements on web-pages is ubiquitous. Without advertisement even this blog could not be offered free of charge. But advertisement can be a real nuisance with its blinking, flickering, moving, and distracting appearance. Sometimes they even contain malware. There are two simple remedies for…
, 2 min read
I upgraded my OnePlus One smartphone from Oxygen 1.0.0 to 1.0.3, see Installing OxygenOS 1.0 on the OnePlus One Smartphone. Download OxygenOS 1.0.3 from OxygenOS 1.0.3 with the latest Stagefright patches, and check MD5. Then upload the zip-file. adb push ~/Download/ONE_12_A.01_150827.zip…
, 1 min read
I learned the hard way that a user in /etc/passwd not having a shell specified in /etc/shells is not able to log-on. On Ubuntu /etc/shells looks like this: /bin/sh /bin/dash /bin/bash /bin/rbash /usr/bin/tmux /usr/bin/screen On Arch it looks like this: /bin/sh /bin/bash So if you provide a user…
, 1 min read
As I commute to work with my e-bike I became more and more interested in bicycle lanes. It looks that this a coming trend in many modern cities. See for example New York, New York's streets? Not so mean any more, a talk by former chief of the department of transport Janette Sadik-Khan under the…
, 1 min read
This is the output of lstopo --of png > ~/tmp/lstopo.png for a machine with an AMD octacore FX 8120, bulldozer architecture, see AMD Bulldozer CPU Architecture Overview. One can just type lstopo, which shows the same in a separate window. lstopo is part of hwloc in Arch or hwloc in…
, 1 min read
Since Android 3 it is no longer possible to access the phone via USB mount. The reason being that Android puts everything into a single partition. As this single partition is always mounted by Android it is not easy to have two users (Android system and PC user) to write on this single partition.…
, 1 min read
Awesome picture from NASA.
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When the CPU is not properly cooled down, then the PC crashes, see below video. The solution for this particular case: Upgrade the BIOS.
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Today I received a free copy of a student-version of Lexware Financial Office Pro 2015 including a license key. Lexware is a financial accounting software which is easy to use and quite well suited for small German enterprises. I installed wine 1.6.2 on Ubuntu 14.04.2 LTS, which consumed almost…
, 1 min read
GSI Helmholtz Centre is a heavy ion research centre near Darmstadt. I visited this research facility on the 06-Jul-2015. It takes a couple of months to acquire a visiting day. Here are some impressions. I highly recommend the facility. Precious beam time is controlled here: Cabling: Combating…