Running programs simultaneously

[awerr54]

I want to run the programs r1-r4 and n1-n4 simultaneously instead of waiting for each one to finish executing,I've been stuck on this for a long time, i went through multi threading for c++ in dev-cpp and the Win API code is quite complicated. How do i execute them simultaneously ?

#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <cstdlib>
#include <conio.h>

using namespace std;
             
int main()
{
    
ifstream od,od2,od3,od4,od5,od6,od7,od8;
ifstream odd,odd2,odd3,odd4,odd5,odd6,odd7,odd8;
string line;
int num[8],nu=0;


system("r1.exe");system("CLS");
system("r2.exe");system("CLS");
system("r3.exe");system("CLS");
system("r4.exe");system("CLS");

system("n1.exe");system("CLS");
system("n2.exe");system("CLS");
system("n3.exe");system("CLS");
system("n4.exe");system("CLS");



od.open("r1.txt");
getline(od,line);
num[nu]=atoi(line.c_str());
nu++;
od.close();

od2.open("r2.txt");
getline(od2,line);
num[nu]=atoi(line.c_str());
nu++;
od2.close();

od3.open("r3.txt");
getline(od3,line);
num[nu]=atoi(line.c_str());
nu++;
od3.close();

od4.open("r4.txt");
getline(od4,line);
num[nu]=atoi(line.c_str());
nu++;
od4.close();

od5.open("n1.txt");
getline(od5,line);
num[nu]=atoi(line.c_str());
nu++;
od5.close();

od6.open("n2.txt");
getline(od6,line);
num[nu]=atoi(line.c_str());
nu++;
od6.close();

od7.open("n3.txt");
getline(od7,line);
num[nu]=atoi(line.c_str());
nu++;
od7.close();

od8.open("n4.txt");
getline(od8,line);
num[nu]=atoi(line.c_str());
nu++;
od8.close();




int best=0;
best=num[0];

for(int i=0;i<nu;i++)
{
if(num[i]>best){best=num[i];}
}


cout << best ;


cin.get();
return 0;
 
}

Then i tried to create a process

STARTUPINFO         siStartupInfo;
    PROCESS_INFORMATION piProcessInfo;

    memset(&siStartupInfo, 0, sizeof(siStartupInfo));
    memset(&piProcessInfo, 0, sizeof(piProcessInfo));

    siStartupInfo.cb = sizeof(siStartupInfo);

    if(CreateProcess("c:\Dev-Cpp\r1.exe",     
 
                    " example.txt",                    
                     0,
                     0,
                     FALSE,
                     CREATE_DEFAULT_ERROR_MODE,
                     0,
                     0,                              
                     &siStartupInfo,
                     &piProcessInfo) == FALSE)

But how do i make multiple programs run simultaneously using create process ?

[MrViggy]

Just call CreateProcess for each exe. The function doesn't block.

Viggy

[awerr54]

Just call CreateProcess for each exe. The function doesn't block.

Viggy

Thanks for the reply,

You mean separate instances of each program like this

    if(CreateProcess("c:\Dev-Cpp\DCS\Decom\r1.exe",     // Application name
                    " example.txt",                 // Application arguments
                     0,
                     0,
                     FALSE,
                     CREATE_DEFAULT_ERROR_MODE,
                     0,
                     0,                              // Working directory
                     &siStartupInfo,
                     &piProcessInfo) == FALSE)
  

    if(CreateProcess("c:\Dev-Cpp\DCS\Decom\r2.exe",     // Application name
                    " example.txt",                 // Application arguments
                     0,
                     0,
                     FALSE,
                     CREATE_DEFAULT_ERROR_MODE,
                     0,
                     0,                              // Working directory
                     &siStartupInfo,
                     &piProcessInfo) == FALSE)

Tried this it does not work,how do i call another instances ?

[MrViggy]

What "doesn't work"? CreateProcess is a non-blocking function. It kicks off the new process, and immediately returns.

Viggy

[S_M_A]

I guess that the processes starts alright but that you are reading the output files to early. Use what's returned in piProcessInfo to wait until the spawned process has exited before reading the file.

See MrViggy's link, http://msdn.microsoft.com/en-us/libr...(v=VS.85).aspx and http://msdn.microsoft.com/en-us/libr...32(VS.85).aspx (or maybe http://msdn.microsoft.com/en-us/libr...(v=VS.85).aspx depending on how you decide to code it)

[Igor Vartanov]

Use what's returned in piProcessInfo to wait until the spawned process has exited before reading the file.

As long as the original point is not only about spawning processes but asynchronous result processing as well, this is where multithreading enters the scene...

[MilesAhead]

If the slave processes are also written by you, then you can have them communicate their status instead of creating a new thread just to wait. For example, by using messages. If you are using already existing programs then your options are more limited.