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james_a_craig | 10 months ago

For some reason the value of Pi given in the C++ code is wrong!

It's given in the source as 3.14159274101257324219 when the right value to the same number of digits is 3.14159265358979323846. Very weird. I noticed when I went to look at the C++ to see how this algorithm was actually implemented.

https://github.com/alexandrefrancois/noFFT/blob/main/src/Res... line 31.

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2YwaZHXV|10 months ago

seems since it's a float it's only 32-bits, and the representation of both 3.14159274101257324219 and 3.14159265358979323846 is the same in IEEE-754: 0x40490fdb

though I agree that it is odd to see, and not sure I see a reason why they wouldn't use 3.14159265358979323846

james_a_craig|10 months ago

Yeah, it’s as if they wrote a program to calculate pi in a float and saved the output. Very strange choice given how many places the value of pi can be found.

pvg|10 months ago

That is a very 'childhood exposure to 8 digit calculators' thing to notice.

james_a_craig|10 months ago

Childhood exposure to pi generation algorithms; the correct version above was from memory.