Double-double arithmetic: 31 digits of precision from two doubles (sample code in C#)

[u/NightElfik]

https://marekfiser.com/blog/double-double-arithmetic/

[u/otac0n]

Why not use IEEE float128?

https://en.wikipedia.org/wiki/Quadruple-precision_floating-point_format

[u/ebfortin → u/otac0n]

The upside of using double double is that you can use the hardware floating point unit of the cpu for somenof the computation. In theory it's faster than a full software implementation of IEEE 128-bits FP. But with all the SIMD extensions out there maybe that's not true anymore with a clever software implementation.

[u/NightElfik → u/otac0n]

In C#? How? Also, it is slower: https://marekfiser.com/blog/double-double-arithmetic/#Comparison-with-__float128

[u/Altruistic-Gap1795]

This is a really interesting approach because double precision is usually enough for most applications but there are some cases where those extra digits matter without wanting the full cost of arbitrary precision math. using two doubles together to extend precision is a clever middle ground