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from the that's-the-combination-to-my-luggage! dept.
https://www.jpl.nasa.gov/edu/news/2016/3/16/how-many-decimals-of-pi-do-we-really-need/
Earlier this week, we received this question from a fan on Facebook who wondered how many decimals of the mathematical constant pi (π) NASA-JPL scientists and engineers use when making calculations:
Does JPL only use 3.14 for its pi calculations? Or do you use more decimals like say: 3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067982148086513282306647093844609550582231725359408128481117450284102701938521105559644622948954930381964428810975665933446128475648233786783165271201909145648566923460348610454326648213393607260249141273724587006606315588174881520920962829254091715364367892590360
We posed this question to the director and chief engineer for NASA's Dawn mission, Marc Rayman. Here's what he said:
(Score: 1) by cyberthanasis on Friday August 16 2019, @07:04AM (1 child)
15 (decimal) significant digits is the best precision you get from IEEE 1754 double precision floating point numbers, used by virtually all contemporary computers.
To that, I would add one more digit, as the binary digits of the double precision value do not correspond to exactly 15 significant decimal digits. And this is exactly the approximation used by NASA.
(Score: 2) by DutchUncle on Friday August 16 2019, @12:52PM
IBM System 360 packed decimal instructions could operate on 32 bytes / 63 digits (plus sign). No decimal point, but back in the slide rule generation the idea of fixed-point / implied-point calculation was normal practice.
Hmm. Multiplying 15 digit numbers gets you 30 digit numbers, so maybe the effective carry-through precision isn't much better.