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Various things in MetaPost

Reading time8 min
Views15K
LaTeX*
Translation
What is the best tool to use for drawing vector pictures? For me and probably for many others, the answer is pretty obvious: Illustrator, or, maybe, Inkscape. At least that's what I thought when I was asked to draw about eight hundred diagrams for a physics textbook. Nothing exceptional, just a bunch of black and white illustrations with spheres, springs, pulleys, lenses and so on. By that time it was already known that the book was going to be made in LaTeX and I was given a number of MS Word documents with embedded images. Some of them were scanned pictures from other books, some were pencil drawings. Picturing days and nights of inkscaping this stuff made me feel dizzy, so soon I found myself fantasizing about a more automated solution. For some reason MetaPost became the focus of these fantasies.



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Total votes 16: ↑15 and ↓1+14
Comments0

Indexes in PostgreSQL — 9 (BRIN)

Reading time18 min
Views9.3K
Postgres Professional corporate blogPostgreSQL*SQL*
Translation
In the previous articles we discussed PostgreSQL indexing engine, the interface of access methods, and the following methods: hash indexes, B-trees, GiST, SP-GiST, GIN, and RUM. The topic of this article is BRIN indexes.

BRIN


General concept


Unlike indexes with which we've already got acquainted, the idea of BRIN is to avoid looking through definitely unsuited rows rather than quickly find the matching ones. This is always an inaccurate index: it does not contain TIDs of table rows at all.

Simplistically, BRIN works fine for columns where values correlate with their physical location in the table. In other words, if a query without ORDER BY clause returns the column values virtually in the increasing or decreasing order (and there are no indexes on that column).

This access method was created in scope of Axle, the European project for extremely large analytical databases, with an eye on tables that are several terabyte or dozens of terabytes large. An important feature of BRIN that enables us to create indexes on such tables is a small size and minimal overhead costs of maintenance.

This works as follows. The table is split into ranges that are several pages large (or several blocks large, which is the same) — hence the name: Block Range Index, BRIN. The index stores summary information on the data in each range. As a rule, this is the minimal and maximal values, but it happens to be different, as shown further. Assume that a query is performed that contains the condition for a column; if the sought values do not get into the interval, the whole range can be skipped; but if they do get, all rows in all blocks will have to be looked through to choose the matching ones among them.

It will not be a mistake to treat BRIN not as an index, but as an accelerator of sequential scan. We can regard BRIN as an alternative to partitioning if we consider each range as a «virtual» partition.

Now let's discuss the structure of the index in more detail.
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Total votes 14: ↑14 and ↓0+14
Comments0

Statistics and monitoring of PHP scripts in real time. ClickHouse and Grafana go to Pinba for help

Reading time6 min
Views5.7K
High performance*PHP*
Tutorial
In this article I will explain how to use pinba with clickhouse and grafana instead of pinba_engine and pinboard.

On the php project pinba is probably the only reliable way to understand what is happening with performance. But usually people start to use pinba only when problems are already observed and it isn't clear where to look in.

Often developers have no idea how many RPS each script has. So they begin to optimize starting from places that seem to have problem.

Someone is analyzing the nginx logs, and someone is slow queries in the database.

Of course pinba would not be superfluous, but there are several reasons why it is not on every project.


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Total votes 16: ↑15 and ↓1+14
Comments0

Indexes in PostgreSQL — 5 (GiST)

Reading time22 min
Views10K
Postgres Professional corporate blogPostgreSQL*SQL*
Translation
In the previous articles, we discussed PostgreSQL indexing engine, the interface of access methods, and two access methods: hash index and B-tree. In this article, we will describe GiST indexes.

GiST


GiST is an abbreviation of «generalized search tree». This is a balanced search tree, just like «b-tree» discussed earlier.

What is the difference? «btree» index is strictly connected to the comparison semantics: support of «greater», «less», and «equal» operators is all it is capable of (but very capable!) However, modern databases store data types for which these operators just make no sense: geodata, text documents, images,…

GiST index method comes to our aid for these data types. It permits defining a rule to distribute data of an arbitrary type across a balanced tree and a method to use this representation for access by some operator. For example, GiST index can «accommodate» R-tree for spatial data with support of relative position operators (located on the left, on the right, contains, etc.) or RD-tree for sets with support of intersection or inclusion operators.

Thanks to extensibility, a totally new method can be created from scratch in PostgreSQL: to this end, an interface with the indexing engine must be implemented. But this requires premeditation of not only the indexing logic, but also mapping data structures to pages, efficient implementation of locks, and support of a write-ahead log. All this assumes high developer skills and a large human effort. GiST simplifies the task by taking over low-level problems and offering its own interface: several functions pertaining not to techniques, but to the application domain. In this sense, we can regard GiST as a framework for building new access methods.
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Total votes 18: ↑16 and ↓2+14
Comments0

Physical unclonable functions: protection for electronics against illegal copying

Reading time7 min
Views5.2K
FPGA*IT Standards*Information Security*Research and forecasts in IT*Manufacture and development of electronics*
Translation

Source: The online counterfeit economy: consumer electronics, a report made by CSC in 2017

Over the past 10 years, the number of fake goods in the world has doubled. This data has been published in the latest Year-End Intellectual Property Rights Review by the US Department of Homeland Security in 2016 (the most current year tracked). A lot of the counterfeiting comes from China (56%), Hong Kong (36%) and Singapore (2%). The manufacturers of original goods suffer serious losses, some of which occur on the electronics market.

Many modern products contain electronic components: clothes, shoes, watches, jewellery, cars.
Last year, direct losses from the illegal copying of consumer electronics and electronic components in the composition of other goods were about $0.5 trillion.

How to solve this problem?
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Total votes 14: ↑14 and ↓0+14
Comments0

Digital Forensics Tips&Tricks: How to Detect an Intruder-driven Group Policy Changes

Reading time2 min
Views6.6K
Information Security*
First of all let's remember a standart group policy precedence: Local — Site — Domain — Organisation Unit (LSDOU). From less specific level to more specific. It means that Local GPO settings will apply first, then Site-level, Domain-level etc. And the last applied (OU GPO) settings have the highest precedence on the resulting system. However, if a domain administrator didn't set some settings in the higher-level GPOs (e.g. Enable/Disable Windows Defender service) but the same settings have been configured on the Local-level GPO — the last ones will be apply. Yes, even the machine is a domain member.

The Local GPO files are located in %systemroot%\System32\GroupPolicy hidden folder and, of course, it has two scopes (located in subfolders): for User and for Computer. Any user (here I mean a «bad guy» of course), having access to this folder(s), can copy a Registry.pol file and check/change a Local GPO settings. An intruder can use a third-part apllication, such as a RegPol Viewer:

image

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Total votes 16: ↑15 and ↓1+14
Comments0

Another way to write cross-platform apps: Neutralinojs internals and comparison with Electron and NW.js

Reading time5 min
Views9.1K
C++*JavaScript*Open source*
From sandbox


I am Shalitha Suranga from Sri Lanka. I started Neutralinojs project with other two members as our research project at university.


Cross-platform application development is extremely useful among software development organizations because a large end-user audience can be targeted. Earlier there were several approaches, such as writing multiple codebases per each platform, writing a single codebase using conditionals for platform selection, or using a programming language which has a cross-platform virtual machine at run-time. There were drawbacks of each like complexity of design, limited low-level accessibility and slow learning rate. Cross-platform application development with web technologies came [1] after. Electron and NW.js are most popular frameworks which allow developers to make cross-platform applications using Javascript. Basically, these popular frameworks combine embedded chromium browser and node run-time [2], [3].


These frameworks are being used to create numerous cross-platform applications. Whereas the community pointed out several unseen drawbacks of these frameworks. Large bundled application size, high memory consumption and long development workflow are the key things which were criticized through internet forums and websites [4], [5], [6], [7], [8]. Table 1.1 shows the advantages and disadvantages of Electron/NW.js.


Table 1.1: Advantages and Disadvantages of Electron/NW,js


Advantages of Electron and NW.js Disadvantages of Electron and NW.js
Development is very easy since Javascript is used Application bundle is considered as bloatware (High disk space usage)
Access native functions via node runtimeSingle codebase for all supported platforms Linux, Windows and macOS High memory consumption and slowness
Many Node modules need to be installed
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Total votes 20: ↑17 and ↓3+14
Comments3

DoT for RPZ distribution

Reading time2 min
Views1.5K
DNS*IT Infrastructure*Information Security*Network technologies*
Just a few months ago there were a lot of buzz because IETF in expedited time frame (about one year) accepted DNS over HTTPS (DoH) as a standard (RFC-8484). The discussions about that are still going on because of its controversy. My personal opinion is that DoH is good for personal privacy (if you know how to use it and trust your DNS provider) but it is a security risk for enterprises. DNS over TLS (DoT) is a better alternative for enterprise customers only because it uses a well-defined TCP port but for personal privacy it is not good because of the same reason (easy to block).
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Total votes 14: ↑14 and ↓0+14
Comments0

10 Things About Technical SEO Every WordPress Site Owner Needs to Know

Reading time7 min
Views1.2K
Search engine optimization*
Any blogger who was brave enough to create his WordPress blog sooner or later faces a question of how to get more visitors. One of the most reasonable ways to attract them is to promote a website in organic search results. This process usually starts from technical optimization that scares most beginners. To overcome your fear of SEO, we've prepared a list of 10 key technical SEO aspects you need to handle.
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Total votes 16: ↑15 and ↓1+14
Comments2

Our new public speech synthesis in super-high quality, 10x faster and more stable

Reading time3 min
Views5K
Natural Language Processing*Voice user interfaces*Machine learning*

hero_image


In our last article we made a bunch of promises about our speech synthesis.


After a lot of hard work we finally have delivered upon these promises:


  • Model size reduced 2x;
  • New models are 10x faster;
  • We added flags to control stress;
  • Now the models can make proper pauses;
  • High quality voice added (and unlimited "random" voices);
  • All speakers squeezed into the same model;
  • Input length limitations lifted, now models can work with paragraphs of text;
  • Pauses, speed and pitch can be controlled via SSML;
  • Sampling rates of 8, 24 or 48 kHz are supported;
  • Models are much more stable — they do not omit words anymore;

This is a truly break-through achievement for us and we are not planning to stop anytime soon. We will be adding as many languages as possible shortly (the CIS languages, English, European languages, Hindic languages). Also we are still planning to make our models additional 2-5x faster.


We are also planning to add phonemes and a new model for stress, as well as to reduce the minimum amount of audio required to train a high-quality voice to 5 — 15 minutes.


As usual you can try our model in our repo or in colab.

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Total votes 13: ↑13 and ↓0+13
Comments0

Q4 2021 DDoS attacks and BGP incidents

Reading time6 min
Views1.1K
Qrator Labs corporate blogNetwork technologies*IT Infrastructure*Information Security*

2021 was an action-packed year for Qrator Labs.

It started with the official celebration of our tenth year anniversary, continued with massive routing incidents, and ended with the infamous Meris botnet we reported back in September.

Now it is time to look at the events of the last quarter of 2021. There are interesting details in the BGP section, like the new records in route leaks and hijacking ASes, but first things first, as we start with the DDoS attacks statistics.

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Total votes 13: ↑13 and ↓0+13
Comments0

Mode on: Comparing the two best colorization AI's

Reading time11 min
Views4K
RUVDS.com corporate blogPython*TensorFlow*Machine learning*Image processing*

This article continues a series of notes about colorization. During today's experiment, we’ll be comparing a recent neural network with the good old Deoldify to gauge the rate at which the future is approaching.

This is a practical project, so we won’t pay extra attention to the underlying philosophy of the Transformer architecture. Besides, any attempt to explain the principles of its operation to a wide public in hand waving terms would become misguiding.

A lecturer: Mr. Petrov! How does a transformer work?
Petrov with a bass voice: Hum-m-m-m.

Google Colorizing Transformer vs Deoldify

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Total votes 15: ↑15 and ↓0+13
Comments0

Active Restore: Can we Recover Faster? Much Faster?

Reading time5 min
Views1.7K
Acronis corporate blogUEFI*Data recovery*Development for Windows*Backup*
Translation
Backing up valuable data is a proven practice, but what if we need to continue work immediately after a natural disaster or other disruptive events, and every minute is important? Our team at Acronis decided to see how quickly we can start an operating system. This is our first post from the Active Restore series. Today I will tell you how we launched our project with Innopolis University, which solutions were studied, and what we are working on today. All the details are under the Cut.

image
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Total votes 9: ↑8 and ↓1+13
Comments0
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