Michel Jean reverse-engineered the numerical integration algorithm used in classic HP scientific calculators by implementing various algorithms in C++ and comparing results. The investigation confirmed that HP calculators use the Romberg-Kahan algorithm, developed by HP mathematician William Kahan and selected in 1979. The algorithm was chosen not for speed but for robustness — it never fails on edge cases, making it ideal for a general-purpose calculator that has no prior knowledge of the input function.
Sort: