Developers Club geek daily blog

Sir Charles Anthony Richard Hoare or just the father of Quicksort, NULL and problem of the having dinner philosophers

1 year, 1 month ago


The knight in education and computer sciences, the man in honor of whom called logic the first who was recognized in the error for one billion dollars, the qsort developer, celebrates today, on January 11, the 82 anniversary. (For certain together with Cnut.)

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New in Wolfram Language | the Analytical solution of partial equations

1 year, 1 month ago

Transfer of a post of Devendra Kapadia "New in the Wolfram Language: Symbolic PDEs".
The code given in article can be downloaded here.
I express huge gratitude to Kirill Guzenko of KirillGuzenko for the help in transfer and preparation of the publication
.
Partial equations (UrChP) play very important role in mathematics and its applications. They can be used for modeling of the real phenomena, such as fluctuations of the tense string, distribution of a heat flow in a rod, in financial areas. The purpose of this article — to slightly open a veil to the world of UrChP (who else is not familiar to those with it) and to acquaint the reader with how it is possible to solve effectively UrChP in Wolfram Language, using new functionality for a solution of boundary value problems in DSolve, and also new DEigensystem function which appeared in version 10.3.

History UrChP goes back to works of the famous mathematicians of the eighteenth century — Euler,Dalambera,Laplace, however development of this area in the last three centuries did not stop. And therefore I will provide both classical, and modern examples of UrChP in article that will allow to consider this knowledge domain under different corners.

Let's begin with consideration of fluctuations of the tense string with a length π, fixed on both ends. Fluctuations of a string can be simulated by means of the one-dimensional wave equation given below. Here u (x, t) — vertical shift of a point of a string with coordinate x in t timepoint:


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Unpacking of the data squeezed by algorithm of Deflate with the fixed Huffman codes on the example of the PNG format

1 year, 1 month ago


Within the next laboratory work we with colleagues faced a problem of analysis of a hexadecimal dump of the PNG file. According to the RFC 2083 standard the PNG format stores the pixel data squeezed by algorithm of Deflate. Therefore at analysis of a dump we needed to unpack compressed data algorithm of Inflate.

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How to predict a stock price: Algorithm of adaptive filtering

1 year, 1 month ago


The group of the Brazilian scientists published the research devoted to creation of the tool for a prediction of behavior of the assets bargaining in stock market. In work the detailed description of a method and method of calculations for similar forecasts is submitted. We present to yours the most interesting moments of this document.

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To a question of timers in OSRV (Outputs)

1 year, 1 month ago
imageIn kratets I will describe contents of article:

There is a cyclic hardware counter which, for example, considers seconds, and there is an interruption on its overflow. We expand notation range with a program method, inkremeniruya value of other cell in interruption. Thus, we have an opportunity to consider and minutes. The essence of a problem is that generally at the same time it is impossible to read value of minutes and seconds, and at consecutive reading there can be an interruption and increase in minutes. Effects: travel in time back.

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Critical errors of design of industrial control system and programming of a PLC

1 year, 1 month ago
Automated control systems for technology process (Industrial control system) on the industrial programmable logic controllers (PLC) on objects of upgrade are implemented into the industries. Again delivered equipment, already by default contains an ACS on a PLC. But quality of design of industrial control system and programming of a PLC sometimes does not correspond to logic and requirements to reliable protection of managed object. In this article I will tell about a typical error of design and programming of normal industrial equipment.

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Tender results on programming on JS: Mail filters

1 year, 1 month ago
Thanks to all participants of our last tender on programming!

We received 408 solutions from 237 different participants (only one participates in tender, the last from solutions from each participant, and we publish the last options). Besides, 7 solutions were sent us or after the termination of term of acceptance of works, or employees of Hola, and we considered them out of the competition.

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Sociology of algorithms: As the financial markets and high-frequency trade (Part 2) are connected

1 year, 1 month ago


Earlier we published in our blog first partresearches of sociology of financial algorithms executed by professor of the Higher school of social sciences of Edinburgh of Donald Mackenzie. Today we present to yours continuation of this interesting work — in the second part it is about different types of HFT requests, dark-pools and the connected ekologiya of the financial markets.

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"Other" logic and reversible calculations

1 year, 1 month ago
камень-ножницы-бумага (на ауребеш) At the end of last year the Google Translate Aurebesh added support of "Galactic language" to an output of a new episode of "Star wars". The truth it turned out that at the choice of this language just there is transfer into English. If to use Chrome or Firefox, then there is a font in which instead of Latin characters aurebesh are substituted, and in IE without special cunnings the English text is output.

Began to remember other examples of creation of "languages of strangers". For example, language Klingonov from "Star Trek" is based on Latin too, but at the same time is worked rather out, has the syntax and the dictionary. Languages of the people of Sredizemya from "Lord of the Rings" – in general separate history.

And still there are such languages as the Linkos which is specially developed by Hans Freudental for interplanetary communication and based on the assumption that the mathematics is a universal language of communication for any reasonable beings.

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Universal Memcomputing Machines as alternative to the Turing machine

1 year, 1 month ago
This article can be considered as loose translation (though rather an attempt to understand) this article. And yes, it is written rather for mathematicians, than for wide audience.

Small spoiler: at the beginning it seemed to me some magic, but then I understood a dirty trick …

Today the Turing machine (further MT) — universal determination of concept of algorithm, so and universal determination of "problem solver". There is a set of other models of algorithm — a lambda calculation, Markov's algorithms, etc., but all of them are mathematically equivalent to MT so though they also are interesting, but in the theoretical world anything is changed significantly.

Generally speaking, there are other models — the Nondeterministic Turing machine, Quantum computers of Turing. However they (so far) are only abstract modeliya, not implemented in practice.

Half a year ago in Science Advances there was interesting article with model of calculations which significantly differs from MT and which is quite possible for implementing in practice (actually article and was how they counted a problem of SSP on real iron).

And yes. The most interesting in this model the fact that, on assurance of authors, in it it is possible to solve (some) problems from the class NP of complete tasks for a polynom of time and memory.

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