GCC 6.1 Compiler Optimization Level Benchmarks

30th May 2016

In Effect of Optimizer in gcc on Intel/AMD and Power8 I measured speed ratios between optimized and non-optimized C code of three on Intel/AMD, and eight on Power8 (PowerPC) for integer calculations. For floating-point calculations the factors were two and three, respectively. Michael Larabel in…

Convert ASCII to Hex and vice versa in C and Excel VBA

23rd May 2016

In Downloading Binary Data, for example Boost C++ Library I already complained about some company policies regarding the transfer of binary data. If the openssl command is available on the receiving end, then things are pretty straightforard as the aforementioned link shows, in particular you then…

No YouTube Videos on Google Chrome v50

2nd May 2016

After upgrading to Google Chrome version 50 I could hear sound in YouTube videos, but no images/video. At first I thought this was a matter just affecting me. Now I noticed that another machine which I upgraded to Google Chrome v50 also lost the ability to watch video in YouTube. This other machine…

Upgrading from OxygenOS 1.0.3 to 2.1.4 on the OnePlus One Smartphone

12th April 2016

This short guide describes how to upgrade your OnePlus One Smartphone from OxygenOS version 1.0.3 to 2.1.4. In this case the initial version of your OS is of no relevant importance -- you can also upgrade from version 1.0.0, but see Installing OxygenOS 1.0 on the OnePlus One Smartphone and…

Performance Comparison C vs. Lua vs. LuaJIT vs. Java

5th April 2016

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…

Slides on OpenMP by Christian Terboven & Dirk Schmidl

23rd March 2016

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…

Performance Comparison of mmap() versus read() versus fread()

3rd February 2016

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…

Statistics of this Blog: Crossed 30.000 Views

24th January 2016

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:

2015 in review – report generated by WordPress

29th December 2015

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…

One Free Invite for the OnePlus X

23rd November 2015

Today I received an invite for the OnePlus X. The code is: GL71-90E4-75E1-DBA7. This invite is valid for 3 days.

nginx: 413 Request Entity Too Large - File Upload Issue

7th November 2015

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 ;…

Small Scale Computing

3rd November 2015

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.,…

Working with Windows Junctions in Python

27th October 2015

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(),…

Photographs from Apollo Mission to Moon

21st October 2015

Brian Koberlein mentioned that NASA provided photos from Apollo moon mission on Flickr.com. Below is one:

Suppressing Advertisement on Web-Pages a.k.a. Ad-Blocking

15th October 2015

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…

Upgrading from OxygenOS 1.0.0 to 1.0.3 on the OnePlus One Smartphone

10th October 2015

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…

Linux pam and /etc/shells

5th October 2015

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…

Urban planning

16th August 2015

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…

Output of lstopo from hwloc

9th August 2015

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…

Accessing Android phone via USB cable

27th July 2015

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.…