Dynamically allocate number of threads depending on number of CPU cores

Question

I am trying to create a multi-threaded CPU benchmarking tool, and I'm unable to do the following: std::thread t[number_of_CPU_cores]; A compiler error is generated when trying to directly assign variable to thread t[] -

Only constant values can be assigned to std::thread t

I therefore tried a stupid idea, which complicated things even more...

Can you help me with creating an array of threads dynamically? (I use the following to determine number of CPU cores)

int CoreCount = atoi(getenv(NUMBER_OF_PROCESSORS));

---

EDIT : Added an MCV example:

Compilation Errors:

• C2672 'std::invoke': no matching overloaded function found <xthread> line 240
• C2893 Failed to specialize function template 'unknown-type std::invoke(_Callable &&,_Types &&...)' <xthread> line 240

Actual Code (very crude implementation - SORRY!!!):

#include<iostream>
#include<cstdlib>
#include<conio.h>
#include<ctime>
#include<thread>

time_t start, endTime;
double IterCount = 0;

void RunBench();

int main()
{
    int CoreCount = atoi(getenv("NUMBER_OF_PROCESSORS"));

    cout<<"Press any key to begin!";
    getch();
    system("cls");
    cout<<"Running benchmark...";

    // Start, End time determined.
    start = time(NULL);
    endTime = start + 120;

    // Initialize n threads(n = Number_of_Processors); Beginning of benchmark.
    switch (CoreCount)
    {
        case 1:
        {
            thread t(RunBench);
            t.join();
            break;
        }
        case 2:
        {
            thread t[2];
            for (int i = 0; i < CoreCount; i++)
                t[i] = thread(RunBench, i); 
            for (int i = 0; i < CoreCount; ++i)
            {
                t[i].join();
            }
            break;
        }
        case 3:
        {
            thread t[3];
            for (int i = 0; i < CoreCount; i++)
                t[i] = thread(RunBench, i);
            for (int i = 0; i < CoreCount; ++i)
            {
                t[i].join();
            }
            break;
        }
        case 4:
        {
            thread t[4];
            for (int i = 0; i < CoreCount; i++)
                t[i] = thread(RunBench, i);
            for (int i = 0; i < CoreCount; ++i)
            {
                t[i].join();
            }
            break;
        }
        case 5:
        {
            thread t[5];
            for (int i = 0; i < CoreCount; i++)
                t[i] = thread(RunBench, i);
            for (int i = 0; i < CoreCount; ++i)
            {
                t[i].join();
            }
            break;
        }
        case 6:
        {
            thread t[6];
            for (int i = 0; i < CoreCount; i++)
                t[i] = thread(RunBench, i);
            for (int i = 0; i < CoreCount; ++i)
            {
                t[i].join();
            }
            break;
        }
        case 7:
        {
            thread t[7];
            for (int i = 0; i < CoreCount; i++)
                t[i] = thread(RunBench, i);
            for (int i = 0; i < CoreCount; ++i)
            {
                t[i].join();
            }
            break;
        }
        case 8:
        {
            thread t[8];
            for (int i = 0; i < CoreCount; i++)
                t[i] = thread(RunBench, i);
            for (int i = 0; i < CoreCount; ++i)
            {
                t[i].join();
            }
            break;
        }
        case 9:
        {
            thread t[9];
            for (int i = 0; i < CoreCount; i++)
                t[i] = thread(RunBench, i);
            for (int i = 0; i < CoreCount; ++i)
            {
                t[i].join();
            }
            break;
        }
        case 10:
        {
            thread t[10];
            for (int i = 0; i < CoreCount; i++)
                t[i] = thread(RunBench, i);
            for (int i = 0; i < CoreCount; ++i)
            {
                t[i].join();
            }
            break;
        }
        case 11:
        {
            thread t[11];
            for (int i = 0; i < CoreCount; i++)
                t[i] = thread(RunBench, i);
            for (int i = 0; i < CoreCount; ++i)
            {
                t[i].join();
            }
            break;
        }
        case 12:
        {
            thread t[12];
            for (int i = 0; i < CoreCount; i++)
                t[i] = thread(RunBench, i);
            for (int i = 0; i < CoreCount; ++i)
            {
                t[i].join();
            }
            break;
        }
    }

    cout<<"Score: "<<IterCount;

    return 0;
}

void RunBench()
{
    int a;
    double ans, i = 0;
    long long fact = 1;

    while (time(NULL) == endTime)
    {
        ans = sqrt(i);
        for (a = 1; a <= i; a++)
            fact = fact*a;
        i++;
        IterCount++;
    }
}

Platform Specifications: - OS: Windows 7 Ultimate SP1 - IDE: Visual Studio 2015 Community Update 2