Duration div mul extras #52813

newpavlov · 2018-07-28T23:01:20Z

Successor of #52556.

This PR adds the following impls:

impl Mul<Duration> for u32 (to allow 10*SECOND in addition to SECOND*10)
impl Mul<f64> for Duration (to allow 2.5*SECOND vs 2*SECOND + 500*MILLISECOND)
impl Mul<Duration> for f64
impl MulAssign<f64> for Duration
impl Div<f64> for Duration
impl DivAssign<f64> for Duration
impl Div<Duration> for Duration (Output = f64, can be useful e.g. for duration/MINUTE)

f64 is chosen over f32 to minimize rounding errors. (52 bits fraction precision vs Duration's ~94 bit)

rust-highfive · 2018-07-28T23:01:23Z

r? @withoutboats

(rust_highfive has picked a reviewer for you, use r? to override)

kennytm · 2018-07-29T03:57:38Z

Could you squash all fixups into a single commit?

newpavlov · 2018-07-29T04:00:46Z

Done.

kennytm · 2018-07-29T04:01:30Z

src/libcore/time.rs

+        if !nanos_f64.is_finite() {
+            panic!("got non-finite value when multiplying duration by float");
+        }
+        if nanos_f64 > (u128::MAX as f64) {


The upper limit is u64::MAX * NANOS_PER_SEC (1.8 × 10²⁸) which is a much smaller number than u128::MAX (3.4 × 10³⁸). If you check for the former you don't need the second secs > (u64::MAX as u128) below.

I was conservative about potential edge effects. So you think it will be enough to just check the following condition?

nanos_f64 > ((u64::MAX as u128)*(NANOS_PER_SEC as u128)) as f64

@newpavlov Yes. But make this a const please.

kennytm · 2018-07-29T04:02:28Z

src/libcore/time.rs

+
+    fn mul(self, rhs: f64) -> Duration {
+        const NPS: f64 = NANOS_PER_SEC as f64;
+        let nanos_f64 = rhs * (NPS * (self.secs as f64) + (self.nanos as f64));


Consider panicking when !(rhs >= 0).

Good point.

rust-highfive · 2018-07-29T04:25:54Z

The job x86_64-gnu-llvm-5.0 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:03:58]    Compiling rustc_lsan v0.0.0 (file:///checkout/src/librustc_lsan)
[00:03:59]    Compiling rustc_asan v0.0.0 (file:///checkout/src/librustc_asan)
[00:04:00]    Compiling rustc_msan v0.0.0 (file:///checkout/src/librustc_msan)
[00:04:01]    Compiling rustc_tsan v0.0.0 (file:///checkout/src/librustc_tsan)
[00:04:02] error[E0599]: no method named `is_sign_negative` found for type `time::Duration` in the current scope
[00:04:02]     |
[00:04:02]     |
[00:04:02] 65  | pub struct Duration {
[00:04:02]     | ------------------- method `is_sign_negative` not found for this
[00:04:02] ...
[00:04:02] 544 |         if rhs.is_sign_negative() {
[00:04:02] 
[00:04:03] error: aborting due to previous error
[00:04:03] 
[00:04:03] For more information about this error, try `rustc --explain E0599`.
---
156608 ./.git/modules/src
149124 ./src/llvm-emscripten/test
145504 ./obj/build/bootstrap/debug/incremental
130636 ./obj/build/bootstrap/debug/incremental/bootstrap-c7ee2tfsizs
130632 ./obj/build/bootstrap/debug/incremental/bootstrap-c7ee2tfsizs/s-f3cg5qdtg9-1vl24hh-11rkeiafedqcr
97532 ./obj/build/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends
77624 ./.git/modules/src/tools
71508 ./src/llvm/lib
70304 ./obj/build/x86_64-unknown-linux-gnu/native

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

scottmcm · 2018-07-30T04:44:38Z

src/libcore/time.rs

+    fn mul(self, rhs: Duration) -> Duration {
+        const NPS: f64 = NANOS_PER_SEC as f64;
+        if self.is_sign_negative() {
+            panic!("duration can not be multiplied by negative float");


This will trigger for a NaN with the sign bit set, which feels like it'd be better reported under non-finite, so maybe just use self < 0 here? Also, multiplying a duration by negative zero seems like it should successfully give a zero duration, not a panic.

scottmcm · 2018-07-30T04:46:08Z

src/libcore/time.rs

+    type Output = Duration;
+
+    fn mul(self, rhs: Duration) -> Duration {
+        rhs.checked_mul(self).expect("overflow when multiplying scalar by duration")


Maybe just use rhs * self to avoid repeating things?

They have different panic messages "multiplying scalar by duration" vs "multiplying duration by scalar"

If having different panic messages is not important, then I'll change it and f64 impl to rhs * self.

newpavlov · 2018-08-02T16:11:15Z

Considering Rust 1.28 release should I change stabilization version to 1.30.0?

kennytm · 2018-08-03T00:31:06Z

@newpavlov Yes.

ollie27 · 2018-09-13T17:13:18Z

src/libcore/time.rs

@@ -30,6 +30,7 @@ const NANOS_PER_MILLI: u32 = 1_000_000;
 const NANOS_PER_MICRO: u32 = 1_000;
 const MILLIS_PER_SEC: u64 = 1_000;
 const MICROS_PER_SEC: u64 = 1_000_000;
+const MAX_NANOS_F64: f64 = ((u64::MAX as u128 + 1)*(NANOS_PER_SEC as u128) - 1) as f64;


The - 1 here doesn't change the value because f64 doesn't have enough precision so this constant ends up being exactly 1ns greater than the largest possible Duration. Either this constant needs to be changed to the next smallest f64 or the check below needs to be changed to nanos >= MAX_NANOS_F64. from_float_secs(2f64.powi(64)) should trigger an overflow but currently it returns a Duration of 0ns.

Ah, yes, it should've been >=. Fixed.

alexcrichton · 2018-09-13T20:12:09Z

@bors: r+

Looks good to me, thanks!

bors · 2018-09-13T20:12:10Z

📌 Commit 2aca697 has been approved by alexcrichton

alexcrichton · 2018-09-13T20:12:34Z

@bors: r-

er actually, mind filing a tracking issue and filling that in?

newpavlov · 2018-09-19T15:41:37Z

Done.

alexcrichton · 2018-09-19T18:12:43Z

@bors: r+

bors · 2018-09-19T18:12:44Z

📌 Commit fd7565b has been approved by alexcrichton

bors · 2018-09-19T19:57:35Z

⌛ Testing commit fd7565b with merge 3c8c357fcf68c8348b3ced62bc0d01b7d68820f7...

bors · 2018-09-19T23:01:06Z

💔 Test failed - status-appveyor

kennytm · 2018-09-20T13:03:27Z

@bors retry 3 hour timeout

…r=alexcrichton Duration div mul extras Successor of rust-lang#52556. This PR adds the following `impl`s: - `impl Mul<Duration> for u32` (to allow `10*SECOND` in addition to `SECOND*10`) - `impl Mul<f64> for Duration` (to allow `2.5*SECOND` vs `2*SECOND + 500*MILLISECOND`) - `impl Mul<Duration> for f64` - `impl MulAssign<f64> for Duration` - `impl Div<f64> for Duration` - `impl DivAssign<f64> for Duration` - `impl Div<Duration> for Duration` (`Output = f64`, can be useful e.g. for `duration/MINUTE`) `f64` is chosen over `f32` to minimize rounding errors. (52 bits fraction precision vs `Duration`'s ~94 bit)

Rollup of 15 pull requests Successful merges: - #52813 (Duration div mul extras) - #53470 (Warn about metadata loader errors) - #54233 (Remove LLVM 3.9 workaround.) - #54257 (Switch wasm math symbols to their original names) - #54258 (Enable fatal warnings for the wasm32 linker) - #54266 (Update LLVM to fix "bool" arguments on PPC32) - #54290 (Switch linker for aarch64-pc-windows-msvc from LLD to MSVC) - #54292 (Suggest array indexing when tuple indexing on an array) - #54295 (A few cleanups and minor improvements to rustc/traits) - #54298 (miri: correctly compute expected alignment for field) - #54333 (Update The Book to latest) - #54337 (Remove unneeded clone() from tests in librustdoc) - #54346 (rustc: future-proof error reporting for polymorphic constants in types.) - #54362 (Pass --batch to gdb) - #54367 (Add regression test for thread local static mut borrows)

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duration div mul extras

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newpavlov force-pushed the duration_mul_div_extras branch from 9b0d0b5 to c24fb12 Compare July 29, 2018 04:00

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newpavlov force-pushed the duration_mul_div_extras branch from 9246687 to 9086139 Compare July 29, 2018 04:33

review update

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newpavlov force-pushed the duration_mul_div_extras branch from 9086139 to 12d8f27 Compare July 29, 2018 04:36

kennytm added T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. relnotes Marks issues that should be documented in the release notes of the next release. labels Jul 29, 2018

add MAX_NANOS_F64 constant

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newpavlov force-pushed the duration_mul_div_extras branch from 5cc5272 to 2ddc2ea Compare July 30, 2018 08:46

change negativity check

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newpavlov force-pushed the duration_mul_div_extras branch from 2ddc2ea to 2c300fa Compare July 30, 2018 09:13

don't duplicate impls

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ollie27 reviewed Sep 13, 2018

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newpavlov mentioned this pull request Sep 19, 2018

Tracking issue for duration_float #54361

Closed

Added tracking issue, fixed check, 1.30 -> 1.31

fd7565b

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 19, 2018

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kennytm mentioned this pull request Sep 20, 2018

Rollup of 15 pull requests #54389

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bors merged commit fd7565b into rust-lang:master Sep 21, 2018

Centril added this to the 1.31 milestone Apr 26, 2019

newpavlov mentioned this pull request Aug 6, 2019

Stabilize duration_float #62756

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Duration div mul extras #52813

Duration div mul extras #52813

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