Developers Club geek daily blog

Data structure 2-3-4 tree

1 year, 10 months ago
When I the first time faced a subject of binary trees in programming, at once found on Habré answers almost to all questions which arose at me, but time went, questions became more and quite recently I found a subject which was not lit on this resource yet - it is 2-3-4 trees. There is excellent article on 2-3 trees in which it is possible to find answers to the questions "What Is a Heap?", "What Is 2-3 Trees", and also information about the main operations with structure therefore I will not repeat and will be passed at once to the main subject.

So, the main difference of 2-3-4 trees from 2-3 consists that they may contain more than three child sites that gives the chance to create four-seater nodes (the nodes having four child sites and three data items). It is possible to see differences visually on a gif image under these the text. On the first slide 2-3 tree, on the second — 2-3-4 are shown.


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Stephen's book of Elementary Introduction to the Wolfram Language Language Tungsten

1 year, 10 months ago

Transfer of a post of Stephen Wolfram "I Wrote a Book — To Teach the Wolfram Language".
I express huge gratitude to Kirill Guzenko of KirillGuzenko for the help in transfer and preparation of the publication

The book "Elementary Introduction to the Wolfram Language Language" is available to you in printed form, is free on the Internet, and also in other forms.



I was not sure that I will sometime write one more book. My latest book — the New type of science — took me more than ten years of the hard concentrated work and is my largest project from all that I ever did.

But some time ago I understood that I should write one more book — such which would acquaint the people not familiar with programming, with the Wolfram Language language and methods of thinking in the computing sphere which are presented by this language.

Result — the book Elementary introduction to the Wolfram Language language which was published today. It is also freely available on the Internet, and in other forms.


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Parallelization of algorithm of Shtrassen on Intel® Xeon Phi(TM)

1 year, 10 months ago
Intel Xeon Phi(TM) coprocessors represent PCI Express the device and have x86 architecture, providing high peak productivities — to 1,2 TFLOPS (one trillion operations with a floating comma per second) to double precision on the coprocessor. Xeon Phi(TM) can ensure simultaneous functioning to 244 flows, and it needs to be considered when programming for achievement of maximum efficiency.

Recently we together with the Intel company conducted small research of efficiency of implementation of algorithm of Shtrassen for the Intel Xeon Phi(TM) coprocessor. To whom subtleties of work with this device and simply loving parallel programming are interesting, I ask under kat.


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Multiplication by a method of the Russian peasants

1 year, 10 months ago
Sometimes this method call "country multiplication", sometimes "Ancient Egyptian", sometimes "Ethiopian", sometimes "multiplication through doubling and halving". Some it is well-known, some – is unclear, but at the same time it is rather useful and can be used not only for multiplication, but also for exponentiation and calculations of matrixes.

Algorithm


  13  x  19 ->     0
   6     38       19
   3     76 ->
   1    152 ->    95
   0    304      247
                 ^^^

Let's write two multiplied numbers nearby – they will become headings of two columns. The third column will contain the increasing sum.

If number in the left column odd, we add number from the right column to the increasing sum. Initially it will be equal to zero.

Then in the left column below we write number from heading, divided in half (with discarding of a remaining balance). 13 / 2 = 6. And in the second column we write the number equal to doubling of column heading, 19*2 = 38.

As number in the left column even, we do not increase the increasing sum.

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Open lecture: problem of feasibility of Boolean formulas

1 year, 10 months ago
image
(A screenshot from the presentation: slideplayer.com/slide/3238789)


We invite all to the open lecture Computer Science of the center devoted to a problem of feasibility of Boolean formulas — one of the most known and important algorithmic tasks. Lecture will take place within a meeting with listeners of an online course "Algorithms: theory and practice. Methods". Time and venue: On December 25, 19:00, BTs of Tayms (St. Petersburg, Kantemirovskaya St. 2A, 4 floor). Participation is free, but registration is required: goo.gl/IiNvV8

Problem of feasibility — a canonical difficult task on which the huge number of researches is carried out: both practical, and theoretical. In particular, annual international conference is devoted to this task. Every year there take place competitions of programs for this task (so-called sat-solver). Such programs are actively used in many application areas. Just several months ago Donald Cnut added volume 4B of the monograph "Programming Art" which third is devoted to a problem of feasibility.

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Optimization of hyper parameters in Vowpal Wabbit by means of the new vw-hyperopt module

1 year, 10 months ago
Hi, Habr! In this article it will be a question of such not really pleasant aspect of machine learning as optimization of hyper parameters. Two weeks ago in very famous and useful Vowpal Wabbit project the vw-hyperopt.py module able to find good configurations of hyper parameters of the Vowpal Wabbit models in spaces of big dimension was poured. The module was developed in DCA (Data-Centric Alliance).


For search of good configurations of vw-hyperopt uses algorithms from pitonovsky library Hyperopt and can optimize hyper parameters it is adaptive by means of the Tree-Structured Parzen Estimators (TPE) method. It allows to find the best optimum, than simple grid search, at the equal number of iterations.

This article will be interesting to all who deal with Vowpal Wabbit, and especially by that who was annoyed with absence in the source code of methods of tuning of numerous handles of models, and or tyunit them manually, or incensed optimization independently.

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Forward, on searches of palindromes 3

1 year, 10 months ago
After seemingly quite good result received in the previous part was only "a local maximum", I for some time threw a problem. I will remind a condition:
"The decimal number 585 is 1001001001 in binary. It is palindromic in both bases. Find n-th palindromic number". Or, in Russian: "The decimal number 585 in binary numeral system looks as 1001001001. It is a palindrome in both numeration systems. Find n-y a similar palindrome".

But existence is considerable faster, with essentially other computing complexity, algorithm haunted me, and eventually I returned to its analysis.

Eventually, the algorithm was not such and difficult, but, in my opinion, very beautiful.

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Detection of insider trade: Algorithms of identification and patterns of illegal transactions

1 year, 10 months ago


How insiders at the exchange specifically behave? Whether their transactions depend on a post in the company (the general or finance director) whether the behavior of insiders changes eventually (whether crisis of 2008 influenced him, for example)?

The group of researchers of institute of technology of Georgia conducted research on the basis of the transactions given about 12 million made by 370 thousand insiders during the period from 1986 to 2012. Identification of patterns of behavior of players in stock market by means of which regulators could find and stop illegal insider trade was the purpose of this work. We present to yours highlights of this document.

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As for 5233 man-hours to create software for the microtomograph

1 year, 10 months ago


I want to tell about the interesting project of the Edison company in more detail. Set the task to write software for the microtomograph for developers, they perfectly coped with it, and then pushed sunflower seeds, bolts, condensers and mol in this tomograph. And this tomograph is necessary to serious uncles to check diamonds and not to buy full of holes.

And still today on December 16, birthday of Johann Radon, Austrian mathematician, rector of the Vienna university which in 1917 entered integral conversion of function of many variables, related to Fourier transform, used today in all tomographs.

Johann Radon was professor of 6 universities (and in one of them even without department), was the president of the Austrian mathematical society. In Austria in honor of it called "Institute of calculus and applied mathematics" and a medal.

How there took place development of software for the tomograph and what problems were solved in process — under a cat.

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Festival of data in the museum of Moscow or as Big Data helps to live and work

1 year, 10 months ago


Hi Habr,

If long ago it was interesting to you how Big Data is applied in different areas of business, science and public administration and it there was a wish to hear from people who are engaged in it, then welcome to the Festival of Data which will take place on December 19 at the Exhibition of the High SMIT Technologies in the Museum of Moscow.

During several business hours of the Festival leading experts of the industry from Yandex, "Schools of data Beeline", Data-Centric Alliance, Avito, state unitary enterprise "NI and PI of the General plan of Moscow, Higher School of Economics National Research University will tell guests of an exhibition about perspectives of use of data analysis in the next several years.

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