, 7 min read
Perl script was running too slow. Rewriting it in C made it 20 times faster. 1. Problem statement. Analyze call-tree dependency in COBOL programs. There are 77 million lines of COBOL code in ca. 30,000 files. These 30,000 COBOL programs could potentially include 74,000 COPY-books comprising 10…
, 6 min read
Many scripting languages, like Awk, Perl, Python, Lua, and so on, have hash-tables already built-in. I needed hashing functionality similar to Perl's hash-variables. In particular I needed lookup, insert, and iterating over all entries. I wrote on hashing in Hashing Just Random Numbers and Hash…
, 1 min read
On 23-Oct-2017 Filippo Mantovani held a talk in Darmstadt on "Mobile technology for production-ready high-performance computing systems: The path of the Mont-Blanc project". Unfortunately I was unable to attend, but Mr. Mantovani sent me his Darmstadt Seminar slides. As his slides and…
, 2 min read
1. Prerequisites Assume one owns $n>0$ different products, $n\in\mathbb{N}$, usually $n\approx 100$. Each product has a cost $c_i>0$, $c_i\in\mathbb{R}$, associated with this ownership, $i=1,\ldots, n$. Let $N=\left\{1,\ldots,n\right\}$, and $\mathbb{P}(N)$ be the powerset of $N$, i.e., the…
, 1 min read
This blog was viewed more than 60.000 times since its inception and had more than 45.000 visitors. I wrote about the development of this blog as follows: 2014/05/07: 5,000 Views 2014/09/10: 10,000 Views 2014/12/27: 15,000 Views 2015/04/23: 20,000 Views 2016/01/24: 30,000 Views 2016/11/12: 40,000…
, 1 min read
An article by Krister Walfridsson on C pointers are not hardware pointers demonstrated that even adjacent integer variables having the same hardware address may compare unequal regarding C pointers. See the following C program: #include <stdio.h> int main(int argc, char *argv[]) { …
, 2 min read
When analyzing longer text, especially if this text was written by oneself, it helps to read the text in a different way, here using a concordance. Assume your text is provided as PDF. Convert PDF to text using pdftotext, which is part of package poppler. Replace line breaks in text file with…
, 1 min read
The discussion forum for Hugo contains a description: Hugo development - how to contribute code. Also see Contributing to Hugo. 1. Preparation First set GOPATH as export GOPATH=$HOME/tmp/H then cd $GOPATH Fetch source with go get time go get -u -v github.com/spf13/hugo takes around 1-2 minutes…
, 1 min read
HP (Hewlett Packard) manufacturer of printers of various sorts (laser, ink) unfortunately again decided to annoy its loyal customers. Repeatedly, HP updated firmware in printers so that they do not work with alternate ink, see for example Disabling 3rd-party ink ensures “best printing…
, 2 min read
In German known as Fünf-Punkte-Satz. This theorem is astounding. It says: If two meromorphic functions share five values ignoring multiplicity, then both functions are equal. Two functions, $f(z)$ and $g(z)$, are said to share the value $a$ if $f(z) - a = 0$ and $g(z) - a = 0$ have the same…
, 1 min read
Recently I had trouble opening PDF documents embedded in Microsoft Word. I speculated about the following reasons for this problem: Adobe Acrobat not installed, I use MuPDF Embedded document simply not "really" embedded but just an icon There is an easy solution. Microsoft Word 2007…
, 1 min read
This blog was viewed more than 50.000 times and had more than 37.000 visitors. I wrote about the development of this blog as follows: 2014/05/07: 5.000 Views 2014/09/10: 10.000 Views 2014/12/27: 15.000 Views 2015/04/23: 20.000 Views 2016/01/24: 30.000 Views 2016/11/12: 40.000 Views The averages…
, 2 min read
As noted in Youtube 500 Internal Server Error today I again noted an "500 Internal Server Error". Normally you would not expect these kind of errors from Google. It says: Sorry, something went wrong. A team of highly trained monkeys has been dispatched to deal with this situation. If you…
, 5 min read
I have written on the Hugo static site generator here. Now I have written a migration program in the Go programming language to convert from WordPress export format to Hugo format. This program wp2hugo.go is in GitHub. It can be freely downloaded and does not need any further dependencies, except,…
, 1 min read
In June 2016 Gustavo Duarte launched Grokbit (dead link). This allows to very easily browse the Linux kernel source tree. This is much better than using Perl, find, grep, etc. for wandering through the code. Added 01-May-2020: Link is dead, so no more grokbit. Added 04-Jan-2024: There is an…
, 18 min read
I purchased an Odroid-XU4 for ca. 80 EUR including power-supply and case from Pollin. The original manufacturer is hardkernel. I intended to use this small ARM computer as a router and firewall. In the past I had used routers from multiple vendors, e.g., Linksys/Cisco, TP-Link, AVM/FritzBox,…
, 1 min read
As described in Commuting to Work with an E-Bike I drive to my work place using an e-bike. As I found out that using a bike is a viable alternative to public transport, I bought a better e-bike after about a year. I bought my first e-bike in March 2015, my second in December 2015, and used it since…
, 2 min read
How fast can you wipe a complete disk? For this I dumped zeros to a MS Windows partition based on an SSD formatted with NTFS. [root@i7 ~]# time dd if=/dev/zero of=/dev/sda1 bs=1M dd: error writing '/dev/sda1': No space left on device 81920+0 records in 81919+0 records out 85898297344 bytes (86 GB,…
, 1 min read
In various forums one reads that one should use dd to copy a ISO image to an USB stick. Although this works, more often you do not want to use a ISO image but rather copy a Linux system at hand. First you mount the root filesystem of the new USB stick, then mount /boot within a chroot. Finally use…
, 2 min read
Hearing all these wonder stories about btrfs I decided to give btrfs a try. Additionally I encrypted my SSD using LUKS. The relevant entries in the Arch WIKI are: Setting up LUKS and btrfs. Here is the list of commands I used. 1. I saved my data from SSD using tar and saved tar-file on…