This is the documentation for the latest (master) development branch of Zephyr. If you are looking for the documentation of previous releases, use the drop-down menu on the left and select the desired version.

SMP Pi

Overview

This sample application calculates Pi independently in many threads, and demonstrates the benefit of multiple execution units (CPU cores) when compute-intensive tasks can be run in parallel, with no cross-dependencies or shared resources.

By changing the value of CONFIG_MP_NUM_CPUS on SMP systems, you can see that using more cores takes almost linearly less time to complete the computational task.

You can also edit the sample source code to change the number of digits calculated (DIGITS_NUM), and the number of threads to use (THREADS_NUM).

Building and Running

This project outputs Pi values calculated by each thread and in the end total time required for all the calculation to be done. It can be built and executed on Synopsys ARC HSDK board as follows:

west build -b qemu_x86_64 samples/smp_pi
west build -t run

Sample Output

Calculate first 240 digits of Pi independently by 16 threads.
Pi value calculated by thread #0: 3141592653589793238462643383279502884197...
Pi value calculated by thread #1: 3141592653589793238462643383279502884197...
...
Pi value calculated by thread #14: 314159265358979323846264338327950288419...
Pi value calculated by thread #15: 314159265358979323846264338327950288419...
All 16 threads executed by 4 cores in 28 msec