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Posted by jpluimers on 2022/02/24
If you do business with for instance Jordan for he first time, then is likely -1 because tomorrow their clock moves forward one hour.
The 2022 daylight saving time changes (summer time / winter time) are at time.is/DST_2022 [Wayback/Archive.is]
[Archive.is] Dr. Jessie Christianstein 👩🏻🔬🧟♀️ on Twitter: “… “
–jeroen
Posted in Algorithms, Development, Software Development | Leave a Comment »
Posted by jpluimers on 2022/01/26
When working with converging algorithms, sometimes floating code can become very slow. That is: orders of magnitude slower than you would expect.
A very interesting answer to [Wayback] c++ – Why does changing 0.1f to 0 slow down performance by 10x? – Stack Overflow.
I’ve only quoted a few bits, read the full question and answer for more background information.
Welcome to the world of denormalized floating-point! They can wreak havoc on performance!!!
Denormal (or subnormal) numbers are kind of a hack to get some extra values very close to zero out of the floating point representation. Operations on denormalized floating-point can be tens to hundreds of times slower than on normalized floating-point. This is because many processors can’t handle them directly and must trap and resolve them using microcode.
If you print out the numbers after 10,000 iterations, you will see that they have converged to different values depending on whether
0or0.1is used.
Basically, the convergence uses some values closer to zero than a normal floating point representation dan store, so a trick is used called “denormal numbers or denormalized numbers (now often called subnormal numbers)” as described in Denormal number – Wikipedia:
…
In a normal floating-point value, there are no leading zeros in the significand; rather, leading zeros are removed by adjusting the exponent (for example, the number 0.0123 would be written as 1.23 × 10−2). Denormal numbers are numbers where this representation would result in an exponent that is below the smallest representable exponent (the exponent usually having a limited range). Such numbers are represented using leading zeros in the significand.
…
Since a denormal number is a boundary case, many processors do not optimise for this.
–jeroen
Posted in .NET, Algorithms, ARM, Assembly Language, C, C#, C++, Delphi, Development, Software Development, x64, x86 | Leave a Comment »
Posted by jpluimers on 2021/12/10
I wonder how many new algorithms were added, as the first 6 were really impressive: [WayBack] IDEA on Twitter: “Excited to announce the IDEA project – an ongoing series of nonverbal algorithm assembly instructions: https://t.co/zOAyfOAv3l… https://t.co/epQfBBdzdF”
While originally scheduling this, these were added:
Posted in Algorithms, Conference Topics, Conferences, Development, Event, IKEA hacks, LifeHacker, Power User, Software Development | Leave a Comment »
Posted by jpluimers on 2021/10/12
For my link archive:
I also need to check out [WayBack] Martin Farach-Colton – Wikipedia, as his algorithm is likely more optimised and more versatile.
–jeroen
Posted in .NET, Algorithms, C#, Development, JavaScript/ECMAScript, Ruby, Scripting, Software Development | Leave a Comment »
Posted by jpluimers on 2021/09/29
[WayBack] We’re approaching the limits of computer power – we need new programmers now | John Naughton | Opinion | The Guardian
Ever-faster processors led to bloated software, but physical limits may force a return to the concise code of the past
So back to optimisation and maybe even assembly language.
Which brings back the days gone by.
–jeroen
Posted in Algorithms, Assembly Language, Development, Software Development | Leave a Comment »
Posted by jpluimers on 2021/09/02
It is always fun to see how Sudoku solving algorithms are created and implemented. This is no exception: [WayBack] Coming Back to Old Problems: How I Finally Wrote a Sudoku Solving Algorithm – DEV Community 👩💻👨💻
For a visual Sudoku solver, I usually take [WayBack] Sudoku Solver by Andrew Stuart. Shows the logic behind solving Sudoku square by square which is part of [WayBack] SudokuWiki.org – Getting Started having many visual explanations on how to solve these puzzles, for instance:
It’s a kind of sudo ku, but visually and never failed me solve one.
–jeroen
Posted in Algorithms, Development, Python, Scripting, Software Development | Leave a Comment »
Posted by jpluimers on 2021/08/05
There is a known saying phrased using cardinal, adverbial or ordinal numbers, and several naming for the first:
Sometimes the second can lead to a pattern.
Posted in Algorithms, Development, LifeHacker, Power User, Software Development | Leave a Comment »
Posted by jpluimers on 2021/07/16
Everyone can learn from an outage. CloudFlare shows how to do it right, for instance on the RegEx-going-wild downtime 2 years ago.
So it’s time to link to that one again: [WayBack] Details of the Cloudflare outage on July 2, 2019
More like these at [WayBack] Post Mortem – The Cloudflare Blog.
More on evaluating regular expressions in linear time:
A method for locating specific character strings embedded in character text is described and an implementation of this method in the form of a compiler is discussed. The compiler accepts a regular expression as source language and produces an IBM 7094 program as object language. The object program then accepts the text to be searched as input and produces a signal every time an embedded string in the text matches the given regular expression. Examples, problems, and solutions are also presented.
Programming Techniques: Regular expression search algorithm
Full Text:
Author: Ken Thompson Bell Telphone Labs, Inc., Murray Hill
Published in:
· Magazine Communications of the ACM CACM Homepage archive Volume 11 Issue 6, June 1968
Pages 419-422
ACM New York, NY, USA
table of contents doi>10.1145/363347.363387
is a method of transforming a regular expression into an equivalent nondeterministic finite automaton (NFA)
The algorithm works recursively by splitting an expression into its constituent subexpressions, from which the NFA will be constructed using a set of rules.[3] More precisely, from a regular expression E, the obtained automaton A with the transition function δ respects the following properties:
- A has exactly one initial state q0, which is not accessible from any other state. That is, for any state q and any letter a, {\displaystyle \delta (q,a)} does not contain q0.
- A has exactly one final state qf, which is not co-accessible from any other state. That is, for any letter a, {\displaystyle \delta (q_{f},a)=\emptyset }.
- Let c be the number of concatenation of the regular expression E and let s be the number of symbols apart from parentheses — that is, |, *, a and ε. Then, the number of states of A is 2s − c (linear in the size of E).
- The number of transitions leaving any state is at most two.
- Since an NFA of m states and at most e transitions from each state can match a string of length n in time O(emn), a Thompson NFA can do pattern matching in linear time, assuming a fixed-size alphabet.
Via [WayBack] Details of the Cloudflare outage on July 2, 2019 | Hacker News
–jeroen
Posted in Algorithms, Development, Power User, RegEx, Software Development | Leave a Comment »
Posted by jpluimers on 2021/07/15
For my link archive: [WayBack] c# – Algorithm to check whether a certain hour falls into a given time period – Stack Overflow answered by [WayBack] kennytm:
Assume you only have the time and not the date.
if end_time >= start_time: return start_time <= current_time <= end_time else: return start_time <= current_time or current_time <= end_time
I totally agree with this comment:
This is brilliant! Thanks a lot. – Martin Dimitrov [WayBack]
I love it when algorithms are simple and elegant.
It reminded me of another scheduling related algorithm: [WayBack] Activity Selection Problem | Greedy Algo-1 – GeeksforGeeks
–jeroen
Posted in .NET, Algorithms, C#, Development, Software Development | Leave a Comment »
Posted by jpluimers on 2021/06/22
I originally posted this in a docker on docker thread, but I think it holds universally:
[WayBack] Jeroen Pluimers on Twitter: “Not having done docker, but having developed enough software to have the impression that as soon as things get hierarchical, things eventually end up in a mess. Somewhere down the road something won’t cope with depth/breadth/size and break badly.”
This despite the cool gif in the reply:
[WayBack] Duffie Cooley on Twitter: “… “
I found the below video files by searching for zzzz
Original thread start:
[WayBack] Duffie Cooley on Twitter: “When you hear Docker in Docker what do you think of? docker socket: Mounting in the underlying docker.sock and allowing a container to make new containers. kernel privs: Giving enough privs to a new container that it can make new containers cause it shares a kernel.”
–jeroen
Posted in Algorithms, Cloud, Containers, Development, Docker, Infrastructure, Kubernetes (k8n), Software Development | Leave a Comment »
PDF
The Wiert Corner - irregular stream of stuff 