Document precision considerations of Duration-float methods#155133
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cuviper wants to merge 1 commit intorust-lang:mainfrom
Open
Document precision considerations of Duration-float methods#155133cuviper wants to merge 1 commit intorust-lang:mainfrom
Duration-float methods#155133cuviper wants to merge 1 commit intorust-lang:mainfrom
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A `Duration` is essentially a 94-bit value (64-bit sec and ~30-bit ns), so there's some inherent loss when converting to floating-point for `mul_f64` and `div_f64`. We could go to greater lengths to compute these with more accuracy, like rust-lang#150933 or rust-lang#154107, but it's not clear that it's worth the effort. The least we can do is document that some rounding is to be expected, which this commit does with simple examples that only multiply or divide by `1.0`. This also changes the `f32` methods to just forward to `f64`, so we keep more of that duration precision, as the range is otherwise much more limited there.
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r? @scottmcm rustbot has assigned @scottmcm. Use Why was this reviewer chosen?The reviewer was selected based on:
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This looks good to me. |
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A
Durationis essentially a 94-bit value (64-bit sec and ~30-bit ns),so there's some inherent loss when converting to floating-point for
mul_f64anddiv_f64. We could go to greater lengths to compute thesewith more accuracy, like #150933 or #154107,
but it's not clear that it's worth the effort. The least we can do is
document that some rounding is to be expected, which this commit does
with simple examples that only multiply or divide by
1.0.This also changes the
f32methods to just forward tof64, so we keepmore of that duration precision, as the range is otherwise much more
limited there.