Fast Factorial Algorithms
http://www.luschny.de/math/factorial/FastFactorialFunctions.htmloading story #48249689
A cached map will do best if you actualy need a fast factorial. There are very little entries before the numbers become pointlessly big.
I hoped this would help me solve some more Project Euler [1] problems. Unfortunately, the algorithms given are not explained in detail, so the learning experience is somewhat mediocre. Then again, I have ChatGPT to elucidate them for me.
This article [2] has some interesting details on the swinging factorial function n≀, but I can't seem to find the essay that it references: "Swing, divide and conquer the factorial", 2008.
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To all commenting about the Sitrling formula, there is a separate page linked at the end for approximations http://www.luschny.de/math/factorial/approx/SimpleCases.html which contains many advanced options to compare for that.
I've always wondered if Stirling(n) can be used to arrive quickly in the vicinity of n!, and then use a search of some kind to get to the exact target.
I wonder if any compiler can rewrite that last one into one of the others.
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