Questionable benchmark code for pipline communication with gnuplot on windows (see https://sourceforge.net/p/gnuplot/bugs/2204/)

GnuplotPerf.cpp

// GnuPlotPerf.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#define NOMINMAX
#include <Windows.h>
#undef near
#undef far

#include <iostream>
#include <sstream>
#include <random>
#include <chrono>

#define BUFSIZE 4096 

PROCESS_INFORMATION piProcInfo;

HANDLE hChildStdInRx; // read
HANDLE hChildStdInTx; // write
HANDLE hChildStdOutRx;
HANDLE hChildStdOutTx;

std::default_random_engine gen;
std::uniform_real_distribution<double> distribution(-200.0, 200.0);

void ThrowWin32Exception(const std::string& message)
{
    DWORD dw = GetLastError();

    std::stringstream what;
    LPSTR errorText = NULL;

    FormatMessageA(
        FORMAT_MESSAGE_ALLOCATE_BUFFER |
        FORMAT_MESSAGE_FROM_SYSTEM |
        FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        dw,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (LPSTR)&errorText,
        0, NULL);

    what << message << " " << errorText;

    LocalFree(errorText);

    throw std::exception(what.str().c_str());
}

void startGnuPlotProcess(int version)
{
    // Set the bInheritHandle flag so pipe handles are inherited. 
    SECURITY_ATTRIBUTES saAttr;
    saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
    saAttr.bInheritHandle = TRUE;
    saAttr.lpSecurityDescriptor = NULL;

    // Create a pipe for the child process's STDOUT. 
    if (!CreatePipe(&hChildStdOutRx, &hChildStdOutTx, &saAttr, 0)) {
        ThrowWin32Exception("Failed to create pipe for stdout.");
    }

    // Ensure the read handle to the pipe for STDOUT is not inherited.
    if (!SetHandleInformation(hChildStdOutRx, HANDLE_FLAG_INHERIT, 0)) {
        ThrowWin32Exception("Failed to disable handle inheritance for stdout pipe.");
    }

    // Create a pipe for the child process's STDIN. 
    if (!CreatePipe(&hChildStdInRx, &hChildStdInTx, &saAttr, 0)) {
        ThrowWin32Exception("Failed to create Pipe for stdin.");
    }

    // Ensure the write handle to the pipe for STDIN is not inherited. 
    if (!SetHandleInformation(hChildStdInTx, HANDLE_FLAG_INHERIT, 0)) {
        ThrowWin32Exception("Failed to disable handle inheritance for stdin pipe.");
    }

    // Create the child process. 
    STARTUPINFOA siStartInfo = {};
    siStartInfo.cb = sizeof(STARTUPINFOA);
    siStartInfo.hStdError = hChildStdOutTx;
    siStartInfo.hStdOutput = hChildStdOutTx;
    siStartInfo.hStdInput = hChildStdInRx;
    siStartInfo.dwFlags |= STARTF_USESTDHANDLES;

    // build command line
    std::string cmd = "";

    switch (version)
    {
    case 528: cmd = "D:\\Temp\\gnuplot\\528\\bin\\gnuplot.exe"; std::cout << "Gnuplot 5.2 patchlevel 8\n"; break;
    case 540: cmd = "D:\\Temp\\gnuplot\\540\\bin\\gnuplot.exe"; std::cout << "Gnuplot 5.4 patchlevel 0\n"; break;
    case 541: cmd = "D:\\Temp\\gnuplot\\541\\bin\\gnuplot.exe"; std::cout << "Gnuplot 5.4 patchlevel 1\n"; break;
    case 542: cmd = "D:\\Temp\\gnuplot\\542\\bin\\gnuplot.exe"; std::cout << "Gnuplot 5.4 patchlevel 2\n"; break;
    case 550: cmd = "D:\\Temp\\gnuplot\\550\\bin\\gnuplot.exe"; std::cout << "Version 5.5 patchlevel 0 last modified 2021-07-12\n"; break;
    default:
        break;
    }

    // Use ACSII to not to deal with std::string LPTSTR conversion
    BOOL bSuccess = CreateProcessA(
        cmd.c_str(),		  // binary
        NULL,        // command line 
        NULL,                 // process security attributes 
        NULL,                 // primary thread security attributes 
        TRUE,                 // handles are inherited 
        0,                    // creation flags 
        NULL,                 // use parent's environment 
        NULL,                 // use parent's current directory 
        &siStartInfo,         // STARTUPINFO pointer 
        &piProcInfo);         // receives PROCESS_INFORMATION 


    if (!bSuccess) {
        ThrowWin32Exception("Failed to create gnuplot process.");
    }
}

void sendData()
{
    const int N = 500000;

    std::cout << "N = " << N << std::endl;

    std::stringstream data;

    data << "set terminal qt" << std::endl;
    data << "splot '-' with points" << std::endl;

    for (size_t i = 0; i < N; i++)
    {
        double x = distribution(gen);
        double y = distribution(gen);
        double z = distribution(gen);

        data << x << " " << y << " " << z << std::endl;
    }

    data << "e" << std::endl;
    data << "unset multiplot" << std::endl;


    DWORD dwRead = data.str().size();
    DWORD dwWritten;
    BOOL bSuccess = FALSE;

    std::cout << "Writing " << dwRead << " bytes" << std::endl;

    auto start = std::chrono::high_resolution_clock::now();

    if (!WriteFile(hChildStdInTx, data.str().c_str(), dwRead, &dwWritten, NULL)) {
        ThrowWin32Exception("Failed to write to stdin.");
    }

    auto finish = std::chrono::high_resolution_clock::now();
    std::chrono::duration<double> elapsed = finish - start;
    std::cout << "Elapsed time: " << elapsed.count() << " s\n";

    std::cout << "Wrote " << dwWritten << " bytes" << std::endl;

    
}

void readData()
{
    DWORD dwRead, dwWritten;
    CHAR chBuf[BUFSIZE];
    BOOL bSuccess = FALSE;
    HANDLE hParentStdOut = GetStdHandle(STD_OUTPUT_HANDLE);

    for (;;)
    {
        bSuccess = ReadFile(hChildStdOutRx, chBuf, BUFSIZE, &dwRead, NULL);
        if (!bSuccess || dwRead == 0) break;

        bSuccess = WriteFile(hParentStdOut, chBuf,
            dwRead, &dwWritten, NULL);
        if (!bSuccess) break;
    }
}

int main()
{
    auto versions = std::vector<int>{ 528, 540, 541, 542, 550 };

    std::cout << "Start.\n";
    startGnuPlotProcess(versions[4]);

    for (int i = 0; i < 1; i++)
    {
        sendData();
        Sleep(500);
    }
    std::cout << "Done.\n";
    readData();

    while (1)
    {

    }
}

Quick and dirty results on Intel Core i5-7600K CPU @ 3.80GHz 3.80 GHz:

Gnuplot 5.2 patchlevel 8
N = 500000
Writing 12589958 bytes
Elapsed time: 1.00804 s
Wrote 12589958 bytes
Done.


Gnuplot 5.4 patchlevel 0
N = 500000
Writing 12589958 bytes
Elapsed time: 1.00536 s
Wrote 12589958 bytes
Done.


Gnuplot 5.4 patchlevel 1
N = 500000
Writing 12589958 bytes
Elapsed time: 0.945512 s
Wrote 12589958 bytes
Done.


Gnuplot 5.4 patchlevel 2
N = 500000
Writing 12589958 bytes
Elapsed time: 0.982691 s
Wrote 12589958 bytes
Done.


Version 5.5 patchlevel 0 last modified 2021-07-12
N = 500000
Writing 12589958 bytes
Elapsed time: 1.11003 s
Wrote 12589958 bytes
Done.

On AMD Ryzen 7 7735HS it takes about 22 seconds (!)
Average CPU speed during tests is ~4.5 GHz
Gnuplot version 6.0 patchlevel rc1