Asklemmy

43811 readers

940 users here now

A loosely moderated place to ask open-ended questions

Search asklemmy 🔍

If your post meets the following criteria, it's welcome here!

Open-ended question
Not offensive: at this point, we do not have the bandwidth to moderate overtly political discussions. Assume best intent and be excellent to each other.
Not regarding using or support for Lemmy: context, see the list of support communities and tools for finding communities below
Not ad nauseam inducing: please make sure it is a question that would be new to most members
An actual topic of discussion

Looking for support?

Looking for a community?

Lemmyverse: community search
sub.rehab: maps old subreddits to fediverse options, marks official as such
!lemmy411@lemmy.ca: a community for finding communities

~Icon~ ~by~ ~@Double_A@discuss.tchncs.de~

founded 5 years ago

MODERATORS

128

What field do you work in, and how many digits of pi do you use? (lemmy.world)

submitted 8 months ago by nycki@lemmy.world to c/asklemmy@lemmy.ml

125 comments fedilink hide all child comments

This article says that NASA uses 15 digits after the decimal point, which I'm counting as 16 in total, since that's how we count significant digits in scientific notation. If you round pi to 3, that's one significant digit, and if you round it to 1, that's zero digits.

I know that 22/7 is an extremely good approximation for pi, since it's written with 3 digits, but is accurate to almost 4 digits. Another good one is √10, which is accurate to a little over 2 digits.

I've heard that 'field engineers' used to use these approximations to save time when doing math by hand. But what field, exactly? Can anyone give examples of fields that use fewer than 16 digits? In the spirit of something like xkcd: Purity, could you rank different sciences by how many digits of pi they require?

you are viewing a single comment's thread
view the rest of the comments

[–] xigoi@lemmy.sdf.org 36 points 8 months ago (1 children)

As a mathematician, I don’t use any digits, but the symbol π.

[–] Ephera@lemmy.ml 13 points 8 months ago (2 children)

As a computer scientist, same, but it's called PI.

It's the computer that does the thing with the digits, not me. 🙃

[–] hallettj@leminal.space 6 points 8 months ago (1 children)

In which case you're probably using a predefined 64-bit floating point number, which I think is accurate to 15 digits.

[–] Ephera@lemmy.ml 5 points 8 months ago

Well, you know what's funny, after writing the comment above, I double-checked what the π constant is called in Rust, as that's what I'm mostly coding with these days.

And well, it actually makes you choose. There's f32::consts::PI and f64::consts::PI. Which I guess, makes sense. If you're calculating with 32-bit floats, you should be aware that π is going to be less precise.
So, yeah, I'm a hoax, computer scientists do need to decide between 32-bit and 64-bit.

In fact, the one time I needed π in Rust, was as a 32-bit float. I built a tiny gravity simulation in a game engine and game engines generally use 32-bit floats...

[–] xigoi@lemmy.sdf.org 5 points 8 months ago (1 children)

I’d like to agree, but writing π with capital letters is heresy.

[–] Ephera@lemmy.ml 6 points 8 months ago

Yeah, math conventions and programming conventions don't always align. As in, basically never...