The author of the answer has set multiple world records for calculating digits of pi. I highly recommend browsing through his answer history. You can learn more from his answers than from entire computer science classes.
C++: http://www.stack-ed.com/#tag/c%2B%2B/user/922184/Mysticial
Performance: http://www.stack-ed.com/#tag/performance/user/922184/Mystici...
Language-Agnostic: http://www.stack-ed.com/#tag/language-agnostic/user/922184/M...
Optimization: http://www.stack-ed.com/#tag/optimization/user/922184/Mystic...
Branch-Prediction: http://www.stack-ed.com/#tag/branch-prediction/user/922184/M...