This was an improved version of my previous pi-calc project, and was made especially for 'super pi second' (as I called it), which was on March 14th 2015, 9:26am/pm + 53 secs :) Like the original project, it calculates thousands of digits of Pi, though it uses lists, which means it's MUCH quicker than the original (~10x) and it overcomes the 10240-character limit for variables. It also shows a countdown to Super Pi Second, if before them both - the one in the morning (9:26:53am), as well as the one in the evening (9.26:53pm) if after the morning one. Choose how many digits (1000 to 500000) and let it go... WARNING: calculating 500000 digits may take a few days! A good number to start with is about 5000. Click through the info slides in project to find out how it works. Fanfare sounds from SoundDogs.com and SoundBible.com. Ding sound (when calculation ends) from SoundFXNow.com. As far as pi calculations go, Scratch is a really slow way to do it because it has to interpret the script and manipulate the really long strings of digits in very inefficient ways. (A decent home computer now can work out a million digits in just a few seconds using more modern algorithms - e.g. see: http://www.apfloat.org/apfloat_java/applet/pi.html ) However, Scratch is considerably faster than my ZX Spectrum was - back in 1984, that took about three weeks to calculate 25000 digits (using the same algorithm as this project), and I coded that in Z80a assembly language. It's also a lot faster than doing it with pen & paper... :) Credit to Klingenstierna for the Machin-like formula used here: pi/4 = 8*atan(1/10) - atan(1/239) - 4*atan(1/515) Credit to Taylor for his series expansion, so the inverse tan function (i.e. atan) can be worked out to high precision using just long addition, subtraction, and simple division: atan(1/x) = 1/x - 1/(3*x^3) + 1/(5*x^5) - 1/(7*x^7) + .... For more information about the method used here, and calculating pi in general, see wikipedia links: http://en.wikipedia.org/wiki/Machin-like_formula http://en.wikipedia.org/wiki/Approximations_of_pi http://en.wikipedia.org/wiki/Chronology_of_computation_of_pi
