How to use multiple cores to run a program

Question

I'm pretty new to ubuntu. I am running a .sh file which is very CPU intensive. I have a computer with 8 cores and I want to use at least four. From my research, I tried using

mpirun -np 4

I could see four CPU's running but it didn't seem to make the program run any faster. So I tried

taskset -c 0,1,2,3 

The program was running alright but it seemed to be using just one core.

What can I do to speed up my program?

Answer 1

A program must be made to use multiple cores. The programmer needs to write a instruction for each core.

If the program you are running don't use it, it never will without a update/upgrade.

What can I do to speed up my program?

You can disable some cores and overclock the one that is left. But first ask yourself if the program needs that speed. Or rewrite the program if possible.