Easiest way to simulate the maximum CPU load?

Question

I have to test an embedded computer for the most extreme conditions of generated heat and current draw, and to do so I want to write a program that employs the CPU resource as much as possible of a quad core CPU (one thread per core). Can you suggest something that would be very CPU hungry?

I have to do this for Linux on a ARMv7 and the language is C or C++, the other examples I have found are either for Windows or not in C/C++.

I am trying something like this on my Windows computer and apparently it is working as it takes 12% of total CPU power (which is a i7 quad core 2 threads per core):

float x = 1.5f;
while (1)
{
    x *= sin(x) / atan(x) * tanh(x) * sqrt(x);
}

I don't know how to make it multi-thread.

Answer 1

Your code is serial. You have eight available threads (4 cores * 2 threads per core = 8 total threads), and your current code uses one of them for 1 thread / 8 available = 12.5% of your CPU. If you have to write your own code (and not use a pre-existing intensive code as already suggested by others), I would recommend putting a #pragma omp parallel above your while loop and compiling with the -fopenmp flag (assuming you are using MinGW, if not, the exact option may vary) so that you use all of the available threads instead.