Impressive stuff, though what struck me was the results, least accuracy wise and what rounding they using:
Pi is 3.14159 26535 89793 238....
So I do wonder what rounding they are using, even truncating as I have (next digit 4 so good place to do that) then can see the last digit should at least be 8, worst case 7 and 6!! There again this may be a convention or result of the methord to calulate Pi.
As for floats, well, for accuracy I'd go with cdecimal right there, though is it as accurate. I suspect it is the formular used that induces the minute error in results.
This is from the decimal benchmarks included in the python source[1], in the recipe given in the decimal documentation[2] the precision is increased for the intermediate steps of the algorithm so it gives the correct end result.
Thank you, out of interest on a appliction I work on every now and then showed a 50% improvement with the code as is, not heavy decimal at all, mostly int's though still a nice speedup.
