jondurrant / rpipico-picalc

Calc the value of PI

RPIPico-PICalc

Calc the value of PI on a Pico.

This is an experiment for my YouTube Channel DrJonEA. I wanted to see the effect of using two cores on the Pico in a barebones model and with FreeRTOS. The workload I am using is to calculate the value of PI to 1000 decimal places,which the Pico does in under a second.

There are a number of approaches to calculating the value of PI. I've used the Spigot-type algorithm and an example called pi_spigot by Iliass Mahjoub.

Clone and Build

Please clone using the --recurse_submodules switch to include the libraries. We both use the pi_spigot library and FreeRTOS Kernel.

Each of the four projects has its own build files. Use normal Pico SDK build process with cmake.

mkdir build
cd build
cmake ..
make

Barebones 1 Core

This is the base example and counts howmany times it can calculate the value of PI in one minute.

Barebones 2 Core

This is simple handcrafted dual core example. So both cores calculate the value of PI and use the Core FIFO to communicate.

1 RTOS

Using a single core for FreeRTOS Kernel to calculate the value of PI. I have two worker threads calculating the value of PI but they are both on the same core. So would expect performance to be a little less than the Barebones 1 Core.

2 RTOS

Using a dual core configuration of FreeRTOS Kernel, making use of the new V11 merged SMP release. I have four worker threads calculating across the two cores.

Results

Model	PIs Calcs
1Core	184
2Core	360
1RTOS	188
2RTOS	336

Surprised that single core FreeRTOS outperforms single core barebones.