Author Archives: dmitriano

An example of heterogeneous lookup with std::unordered_set in C++20

std::unordered_set has a template find function in C++20. To make it work I define a custom hash and a custom equality compares as follows:

struct BotSettings
{
    std::string type;
    std::string name;
    bool started;
};
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How my trading bot buys the cryptocurrency

I used a simple algorithm a got an interesting effect: the bot often buys at the peaks of the falling price. Below I provided some examples of buying the cryptocurrency on Binance crypto exchange:

DASH/USDT:

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‘Invalid UTF-8 code encountered.’ close reason with QWebSocket

I get close reason: ‘Invalid UTF-8 code encountered.’ (code=1007) with QWebSocket in the following scenario:

  • I connect to Binance stream wss://stream.binance.com:9443/stream with QWebSocket::open.
  • Successfully receive messages for some time period (a few hours).
  • Binance disconnects me when its servers load increases (because I have low-priority API) and I get close reason code=1000 that indicates a normal closure.
  • Try to reconnect multiple times by calling QWebSocket::open again, but Binance closes the connection with close reason ‘Invalid UTF-8 code encountered.’ (code=1007) that indicates that an endpoint is terminating the connection because it has received data within a message that was not consistent with the type of the message (e.g., non-UTF-8 [RFC3629] data within a text message).
  • Restart the application manually and connect successfully.

The difficulty of reproducing the bug is that Binance disconnects me rarely (once a day, for example) and experimentation with disconnecting the network cable from my machine does not have this effect, after I connect the cable back, QWebSocker reconnects successfully. When I disconnect the network cable I get Error: ‘Unknown error’ (code=-1), Close reason: ” (code=1000).

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My first trade with my simple Binance bot

It calculates the difference between 2.5 hour moving average (MA) and the current price, when the difference exceeds the threshold it buys:

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Array subscript -N is outside array bounds warning in GCC11

Consider the code below with UB:

template <class Derived>
class A
{
public:

    Derived * get() { return static_cast<Derived *>(this);}

private:

    int m_a;
};

class B
{
public:

    double m_b;
};

class X : public B, public A<X>
{
public:

    int m_x;
};

int main()
{
    A<X> a;
    std::cout << a.get();
    return 0;
}
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Disabling power button on Windows 10

When you mistakenly press power button your Windows 10 machine surprisingly shuts down. Switch it off with the following steps:

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Compiling Awl on Ubuntu 18 and 20 with GCC 11

Below I provided the instruction on how to build Awl on Ubuntu 18 and 20.

On Ubuntu 18 you do an extra step to install CMake version >= 3.12:

wget -O - https://apt.kitware.com/keys/kitware-archive-latest.asc 2>/dev/null | sudo apt-key add -
sudo apt-add-repository 'deb https://apt.kitware.com/ubuntu/ bionic main'
sudo apt update

Then do the following steps on both Ubuntu 18 and 20:

sudo apt install cmake
cmake --version
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Earned 50$ with some unknown coins on Binance

Coins FIS, BADGER and TORN did 3x, 2x and 2x respectively and I earned 50$ with my trading bot:

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Multi-Processor in Visual Studio

It is /MP:

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Investigating how to find the candles on a price chart

The basic idea is to calculate the difference with 10 minutes (600 seconds) moving and the current price, for example.

ASR/USDT:

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