Use constant for 180/π in f32::to_degrees #61
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The current `f32::to_degrees` implementation uses a division to calculate 180/π, which causes a loss of precision. Using a constant is still not perfect (implementing a maximally-precise algorithm would come with a high performance cost), but improves precision with a minimal change. This is a backport from [`std`]. [`std`]: rust-lang/rust@e34c31b
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Just for reference, we also discussed the implication that some inputs are now less accurate, in rust-lang/rust#48617. But the rounding is more correct in general, and here we forward to |
cuviper
reviewed
Apr 10, 2018
src/float.rs
Outdated
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| #[test] | ||
| fn to_degrees_rounding() { | ||
| assert_eq!(1_f32.to_degrees(), 57.2957795130823208767981548141051703); |
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When we forward to std, this fails on Rust 1.8 since it lacks rust-lang/rust#47919. Maybe just limit this test to no-std builds? (with a comment explaining this reason)
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Strange, 1.8 still failed! |
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Solved by explicitly calling bors r+ |
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May 4, 2018
61: Use constant for 180/π in f32::to_degrees r=cuviper a=vks The current `f32::to_degrees` implementation uses a division to calculate 180/π, which causes a loss of precision. Using a constant is still not perfect (implementing a maximally-precise algorithm would come with a high performance cost), but improves precision with a minimal change. This is a backport from [`std`]. [`std`]: rust-lang/rust@e34c31b Co-authored-by: Vinzent Steinberg <vinzent.steinberg@gmail.com> Co-authored-by: Josh Stone <cuviper@gmail.com>
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Thanks for the fix! I forgot about this PR... |
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The current
f32::to_degreesimplementation uses a division tocalculate 180/π, which causes a loss of precision. Using a constant is
still not perfect (implementing a maximally-precise algorithm would come
with a high performance cost), but improves precision with a minimal
change.
This is a backport from
std.