Roman's knowledgebase

In information theory and computer science, the Levenshtein distance is a metric for measuring the amount of difference between two sequences (i.e. an edit distance). The term edit distance is often used to refer specifically to Levenshtein distance.

The Levenshtein distance between two strings is defined as the minimum number of edits needed to transform one string into the other, with the allowable edit operations being insertion, deletion, or substitution of a single character. It is named after Vladimir Levenshtein, who considered this distance in 1965. (wikipedia with code, russian version)

• Levenshtein Distance, in Three Flavors (java applet)
• Damerau–Levenshtein distance
• Levenstein distance.beam (slideshare presentation)

QThread was designed and is intended to be used as an interface or a control point to an operating system thread, not as a place to put code that you want to run in a thread. We object-oriented programmers subclass because we want to extend or specialize the base class functionality. The only valid reasons I can think of for subclassing QThread is to add functionality that QThread doesn’t have, e.g. perhaps providing a pointer to memory to use as the thread’s stack, or possibly adding real-time interfaces/support. Code to download a file, or to query a database, or to do any other kind of processing should not be added to a subclass of QThread; it should be encapsulated in an object of it’s own.

You’re doing it wrong…

// create the producer and consumer and plug them together
Producer producer;
Consumer consumer;

bool bOk = producer.connect(&consumer,
                            SIGNAL(consumed()),
                            SLOT(produce()));
Q_ASSERT(bOk);
bOk = consumer.connect(&producer,
                       SIGNAL(produced(QByteArray *)),
                       SLOT(consume(QByteArray *)));
Q_ASSERT(bOk);

// they both get their own thread
QThread producerThread;
producer.moveToThread(&producerThread);

QThread consumerThread;
consumer.moveToThread(&consumerThread);

// go!
producerThread.start();
consumerThread.start();

Reference: Threading without the headache or QThread’s no longer abstract (see attached file)

Optimization manuals and test programs for measuring clock cycles in C++ and assembly code.

Note: Based on some feedback I should clarify that this does not cover C99 syntax

Even though the C programming language has been around since the late 1960’s, many programmers still have trouble understanding how C declarations are formed. This is not unsurprising due to the complexity that can arise when mixing pointer, array and function-pointer declarations.

In this posting we shall look at some complex declarations to try and understand them by considering how they are formed. The intent is not so you can go off and write wonderfully complex declarations, but more hopefully you may actually be able to understand someone else’s code. Finally we shall look at how most complex declarations can be easily simplified.

Here I’m going to focus on object declarations/definitions rather than functions. Also, in this posting I’m not going to examine structure, union or enumeration specifies. They’ll keep for another day.

The upcoming C++ standard (C++0x) will support multithreading and concurrency both as an inherent part of the memory model, and as part of the C++ Standard Library. ”Multithreading and Concurrency” (Anthony Williams):

• Multithreading in C++0x Part 1: Starting Threads
• Multithreading in C++0x Part 2: Starting Threads with Function Objects and Arguments
• Multithreading in C++0x Part 3: Starting Threads with Member Functions and Reference Arguments
• Multithreading in C++0x Part 4: Protecting Shared Data
• Multithreading in C++0x Part 5: Flexible locking with std::unique_lock<>
• Multithreading in C++0x part 6: Lazy initialization and double-checked locking with atomics
• Multithreading in C++0x part 7: Locking multiple mutexes without deadlock
• Multithreading in C++0x part 8: Futures, Promises and Asynchronous Function Calls

Also Herb Sutter is a leading authority on software development. He is the best selling author of several books including Exceptional C++ and C++ Coding Standards, as well as hundreds of technical papers and articles, including “The Free Lunch Is Over” which coined the term “concurrency revolution.”

Effective Concurrency: Prefer Futures to Baked-In “Async APIs”

[slideshare id=3098055&doc=qt003smartpointers-100207135014-phpapp02]

Andrei Alexandrescu gives his keynote presentation, “Iterators Must Go!” at BoostCon 2009. Slides are available here (pdf).

Permalink

Iterators Must Go (Google Docs)

#include <vector>
#include <string>
#include <iostream>
#include <fstream>
#include <algorithm>
#include <iterator>

int main(int argc, char* argv[])
{
    std::vector<std::string> v;
    std::ifstream f("e:/test.txt");
    if(f.is_open())
    {
        std::copy(std::istream_iterator<std::string>(f),
                  std::istream_iterator<std::string>(),
                  std::back_inserter(v));
    }
    // проверка
    std::copy(v.begin(), v.end(),
              std::ostream_iterator<std::string>(std::cout, "\n"));

    return 0;
}

rsdn.ru

#define YEAR ((((__DATE__ [7] - '0') * 10 + (__DATE__ [8] - '0')) * 10 \
              + (__DATE__ [9] - '0')) * 10 + (__DATE__ [10] - '0'))

#define MONTH (__DATE__ [2] == 'n' ? 0 \
               : __DATE__ [2] == 'b' ? 1 \
               : __DATE__ [2] == 'r' ? (__DATE__ [0] == 'M' ? 2 : 3) \
               : __DATE__ [2] == 'y' ? 4 \
               : __DATE__ [2] == 'n' ? 5 \
               : __DATE__ [2] == 'l' ? 6 \
               : __DATE__ [2] == 'g' ? 7 \
               : __DATE__ [2] == 'p' ? 8 \
               : __DATE__ [2] == 't' ? 9 \
               : __DATE__ [2] == 'v' ? 10 : 11)

#define DAY ((__DATE__ [4] == ' ' ? 0 : __DATE__ [4] - '0') * 10 + (__DATE__ [5] - '0'))

#define DATE_AS_INT (((YEAR - 2000) * 12 + MONTH) * 31 + DAY)

int main (void)
{
  printf ("%d-%02d-%02d = %d\n", YEAR, MONTH + 1, DAY, DATE_AS_INT);
  return 0;
}

• download latest Boost version
• unpack it
• run “Visual Studio 2008 Command Prompt” bat file

build bjam

• go to %BOOST%/tools/jam/src folder
• run build.bat file
• copy bjam.exe file to %BOOST%/bin folder from %BOOST%/tools/jam/src/bin.ntx86 folder

build boost

• go to %BOOST% folder
• compile Boost using bjam.exe:

bin\bjam.exe –build-dir=”C:\Dev\Libs\boost\build-boost” –toolset=msvc –build-type=complete stage