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From what I have read, it appears that the most efficient methods of calculating $ \pi $ are Machin-like formulae. And it is known that certain formulas are more efficient than others.

Are there any theoretical properties (rates of convergence, etc) of these formulas that make them more efficient than others?

Like, why is $$ \frac{\pi}{4} = 183\arctan\frac{1}{239} + 32\arctan\frac{1}{1023} - 68\arctan\frac{1}{5832} + 12\arctan\frac{1}{110443} - 12\arctan\frac{1}{4841182} - 100\arctan\frac{1}{6826318} $$ more efficient than $$ \frac{\pi}{4} = \arctan\frac{1}{2} + \arctan\frac{1}{3} $$ (as claimed by Wikipedia)

Or is this a purely empirical result?

I presume that the calculation of arctan is done using the Maclaurin series.

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    Many of the recent record computations use algorithms that are not at all Machin-like. In Machin-like methods, it is basically Maclaurin series, with speedup techniques. Note that if we have a "long" Machin-like formulas, like the $6$-term one you quote, the individual terms can be computed *in parallel*.2012-06-04

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