, 17 min read
1. Semistabilitätsfunktionale in Matrixdarstellung 2. Bemerkungen zum Spijkerschen Stabilitätsfunktional 1. Semistabilitätsfunktionale in Matrixdarstellung Mit Ausnahme der Booleschen Algebra wird keine Theorie in der Mathematik universeller benutzt als die lineare Algeba. Es gibt kaum eine…
, 19 min read
1. Das modifizierte Newton-Verfahren und Spezialisierungen 2. Die Divergenzsätze von Hughes Hallett 3. Die Experimente von Byrne/Hindmarsh/Jackson/Brown Einer der ganz zentralen Bestandteile eines Programmes, basierend auf Verfahren mit impliziten Stufen, ist die Auflösung der…
, 58 min read
1. Einführung und grundlegende Begriffe 2. Die Lemmata von Gronwall 3. Notation und Darstellungssatz für Differenzengleichungen 4. Stabilitätsfunktionale für feste Schrittweiten 5. Projektorstabilitätsfunktionale 6. Nichtäquidistante Gitter 7. Die Eigenwerte gewisser tridiagonaler…
, 23 min read
1. Konditionszahlen von Matrizen 2. Elementare Zeilen- und Spaltenoperationen 3. Die $LU$-Zerlegung 4. Die Gauß-Elimination Bei jedem Iterationsschritt eines Newton-Raphson-Verfahrens, bzw. bei jeder Aktualisierung der Iterationsmatrix beim Newton-Kantorovich Iterationsverfahren, fällt die…
, 6 min read
1. Projektor Sei eine lineare Mannigfaltigkeit ${\cal M}\subseteq\mathbb{C}^n$ aufgespannt durch die $s$ linear unabhängigen Vektoren $a_1,\ldots,a_s\in\mathbb{C}^n$. Sei $A=(a_1,\ldots,a_s)\in\mathbb{C}^{n\times s}$. Es gilt $$ % Mehrfache Indizes für Minoren: % #1: Anzahl der Indizes, #2:…
, 2 min read
I turned 60 this year. I had written a similar post ten years ago: Turning 50 - Now what? What has happened in the last ten years? The last time I wrote: I am married and have three children. All three children show interest in society and technology, and will likely find their way through life.…
, 6 min read
This blog offered to switch betwen light and dark mode. But this choice was not stored anywhere. So any page you clicked on, you had to choose dark mode again. Now I store this choice in localStorage on the client. While cookies could also be used for storing this choice, they are not needed for…
, 1 min read
I stumbled upon below error message from the IBM COBOL compiler for mainframe: IGYRC5108-U COBOL COMPILER TERMINATING: UNCORRECTABLE PROGRAM INTERRUPT CONDITION. The COBOL program was not fully compiled but compilation stopped midway. Further messages from the compile run: PROGRAM CHECK,…
, 1 min read
I am now a member of the 1MB club. The members must have websites with size below 1 MB. This new membership is not surprising as I am already a member of the two clubs: Member of 512KB club Member of 250KB club This 1MB club has 781 members as of today. Becoming member there is by using: git…
, 4 min read
In the previous post Example Theme for Simplified Saaze: Wendt I demonstrated the transition from a website using WordPress to Simplified Saaze. This very blog, which you are reading right now, also uses Simplified Saaze. This post shows how much better performance-wise this transition was. The…
, 12 min read
Another theme for Simplified Saaze called "Wendt". You can inspect it here. It offers below features: Responsive with media breaks for large and small screens, and for printing. Top menu with submenus. Two column using CSS grid, "Holy Grail Layout". Multiple blogs: Each…
, 5 min read
1. Task at hand. COBOL programs reads UNIX timestamps as input. Output should be the values of year, month, day, hour, minutes, seconds. In C this is just gmtime(). gmtime accepts time_t and produces struct tm: struct tm *gmtime(const time_t *timep); On mainframe, however, it is sometimes a little…
, 7 min read
1. Task at hand. Install H2O web-server on Arch Linux. H2O is a web-server written by Kazuho Oku et al. It supports: HTTP/1 and HTTP/1.1, HTTP/2, HTTP/3 ("QUIC"), FastCGI, therefore PHP-FPM, Reverse proxy, Builtin mruby, though, that crashes. In benchmarks it ranks at the top…
, 2 min read
In the old UNIX days the core file was written where the offending program was started. The only prerequisite was that there was no limit imposed. Limits can be checked by $ ulimit -a -t: cpu time (seconds) unlimited -f: file size (blocks) unlimited -d: data seg size…
, 4 min read
9th April is CSS Naked Day. A day where you do not use CSS on your web-site. In 2024 I participate in this day, i.e., I will deactivate the CSS on this blog. From the CSS Naked Day: The idea behind CSS Naked Day is to promote web standards. Plain and simple. This includes proper use of HTML,…
, 2 min read
How can you detect whether a Linux binary was compiled with gcc -fomit-frame-pointer Unfortunately the ELF itself does not contain a flag, which tells you that. But looking at the assembler code can give you the answer. First disassemble the code with objdump -d Check the disassembly for below…
, 2 min read
In the year 2020 in the blog post Chinese Hackers I noticed that China tries the most to hack my Linux machines. These attempts look like this: $ lastb a ssh:notty 209.97.163.130 Tue Mar 5 13:07 - 13:07 (00:00) sftpuser ssh:notty 93.123.39.2 Tue Mar 5 13:05 - 13:05 …
, 5 min read
I tried to install IBM COBOL for Linux multiple times. I tried to install it on Arch Linux, which is the Linux I use: Installing IBM COBOL for Linux on Arch Linux in 2021 Testing COBOLworx gcc-cobol #2 in 2023 Initially I succeeded in installing the IBM compiler in 2021. The IBM compiler compared…
, 6 min read
This blog uses Simplified Saaze as its static site generator. Generating all 561 HTML pages takes 0.25 seconds. The environment used is as in below table. Type Value CPU AMD Ryzen 7 5700G RAM 64 GB OS Arch Linux 6.7.6-arch1-1 #1 SMP PREEMPT_DYNAMIC PHP PHP 8.3.3 (cli) PHP with…
, 1 min read
Ronalds Vilcins, in his article RSS feeds for your Github releases, tags and activity, provides a handy overview of some GitHub RSS feeds. I reproduce them here…