delta/go-git.git/src/strings, branch dev.cmdgo

bytes, strings: optimize Trim for single byte cutsets

2021-08-25T19:29:15+00:00

Using the latest version of all modules known by the module proxy,
we determine that for all Trim usages (and related functionality):
* 76.6% have cutsets of len=1, and
* 13.4% have cutsets of len=2.

Given that a vast majority of usages only have a cutset of len=1,
we should more heavily optimize for that situation.
Previously, there was some optimization for cutsets of len=1,
but it's within the internal makeCutsetFunc function.
This is sub-optimal as it incurs an allocation in makeCutsetFunc
for the closure over that single byte.

This CL removes special-casing of one-byte cutsets from makeCutsetFunc
and instead distributes it directly in Trim, TrimRight, and TrimLeft.
Whether we should distribute the entire ASCII cutset logic into Trim
is a future CL that should be discussed and handled separately.
The evidence for multibyte cutsets is not as obviously compelling.

name                old time/op  new time/op  delta
bytes/TrimByte-4    84.1ns ± 2%   7.5ns ± 1%  -91.10%  (p=0.000 n=9+7)
strings/TrimByte-4  86.2ns ± 3%   8.3ns ± 1%  -90.33%  (p=0.000 n=9+10)

Fixes #46446

Change-Id: Ia0e31a8384c3ce111ae35465605bcec45df2ebec
Reviewed-on: https://go-review.googlesource.com/c/go/+/323318
Trust: Joe Tsai 
Run-TryBot: Joe Tsai 
Reviewed-by: Brad Fitzpatrick 
TryBot-Result: Go Bot

strings: smarter growth of temporal buffer and avoid copying on return

2021-08-22T23:49:55+00:00

The implementation for single strings had two optimization opportunities:
1. Grow the temporary buffer by known size before appending.
2. Avoid a full copy of the result since the underlying buffer won't be mutated afterward.
Both things were leveraged by using a Builder instead of a byte slice.

Relevant benchmark results:

        name           old time/op    new time/op    delta
        SingleMatch-8    32.0µs ± 3%    26.1µs ± 3%  -18.41%  (p=0.000 n=9+10)

        name           old speed      new speed      delta
        SingleMatch-8   469MB/s ± 3%   574MB/s ± 3%  +22.56%  (p=0.000 n=9+10)

        name           old alloc/op   new alloc/op   delta
        SingleMatch-8    81.3kB ± 0%    49.0kB ± 0%  -39.67%  (p=0.000 n=10+10)

        name           old allocs/op  new allocs/op  delta
        SingleMatch-8      19.0 ± 0%      11.0 ± 0%  -42.11%  (p=0.000 n=10+10)

Change-Id: I23af56a15875206c0ff4ce29a51bec95fd48bb11
GitHub-Last-Rev: 403cfc3c2794b5da27792c51999417a2a052b365
GitHub-Pull-Request: golang/go#47766
Reviewed-on: https://go-review.googlesource.com/c/go/+/343089
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Go Bot 
Reviewed-by: Ian Lance Taylor 
Trust: Robert Griesemer

bufio, bytes, strings: handle negative runes in WriteRune

2021-02-24T04:01:25+00:00

Updates #43254

Change-Id: I7d4bf3b99cc36ca2156af5bb01a1c595419d1d3c
Reviewed-on: https://go-review.googlesource.com/c/go/+/280492
Reviewed-by: Emmanuel Odeke 
Reviewed-by: Rob Pike 
Trust: Emmanuel Odeke 
Run-TryBot: Emmanuel Odeke 
TryBot-Result: Go Bot

strings: complete Reader doc string

2020-10-30T00:23:50+00:00

Follow-up on https://golang.org/cl/247523.

Change-Id: I9e91a6d77271e640d84851f2e2a4c6d2150a2b43
Reviewed-on: https://go-review.googlesource.com/c/go/+/266438
Trust: Robert Griesemer 
Reviewed-by: Ian Lance Taylor

strings: complete documentation of strings.Reader

2020-10-30T00:03:40+00:00

There is no documentation on a number of methods of the strings.Reader
struct, so this change adds documentation referring to the relevant
io.* interfaces implemented. This is consistent with pre-existing
documentation in this struct.

Fixes #40381

Change-Id: I3dec65ecafca5b79d85d30a676d297e5ee9ab47e
GitHub-Last-Rev: f42429946a2b90b9fbfbd1ea5943f0c50e0439b5
GitHub-Pull-Request: golang/go#40654
Reviewed-on: https://go-review.googlesource.com/c/go/+/247523
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Go Bot 
Reviewed-by: Robert Griesemer 
Trust: Ian Lance Taylor

all: update references to symbols moved from io/ioutil to io

2020-10-20T18:41:18+00:00

The old ioutil references are still valid, but update our code
to reflect best practices and get used to the new locations.

Code compiled with the bootstrap toolchain
(cmd/asm, cmd/dist, cmd/compile, debug/elf)
must remain Go 1.4-compatible and is excluded.
Also excluded vendored code.

For #41190.

Change-Id: I6d86f2bf7bc37a9d904b6cee3fe0c7af6d94d5b1
Reviewed-on: https://go-review.googlesource.com/c/go/+/263142
Trust: Russ Cox 
Run-TryBot: Russ Cox 
TryBot-Result: Go Bot 
Reviewed-by: Emmanuel Odeke

strings: optimize Replace by using a strings.Builder

2020-08-17T04:08:35+00:00

name        old time/op    new time/op    delta
ReplaceAll     162ns ±26%     134ns ±26%  -17.44%  (p=0.014 n=10+10)

name        old alloc/op   new alloc/op   delta
ReplaceAll     32.0B ± 0%     16.0B ± 0%  -50.00%  (p=0.000 n=10+10)

name        old allocs/op  new allocs/op  delta
ReplaceAll      2.00 ± 0%      1.00 ± 0%  -50.00%  (p=0.000 n=10+10)

Change-Id: Ia8377141d3adb84c7bd94e511ac8f739915aeb40
Reviewed-on: https://go-review.googlesource.com/c/go/+/245197
Run-TryBot: Martin Möhrmann 
TryBot-Result: Gobot Gobot 
Reviewed-by: Keith Randall

bytes, strings: align requirements for functions passed to FieldFuncs

2020-04-29T19:58:47+00:00

golang.org/cl/229763 removed the documentation of requirements of
the function passed to FieldsFunc. The current implementation does
not require functions to return consistent results but this had not
been the case for previous implementations.

Add the requirement for consistent results back to the documentation
to allow for future implementations to be more allocation efficient
for an output with more than 32 fields. This is possible with a two
pass algorithm first determining the number of fields used to allocate
the output slice and then splitting the input into fields.

While at it align the documentation of bytes.FieldsFunc with
strings.FieldFunc.

Fixes #38630

Change-Id: Iabbf9ca3dff0daa41f4ec930a21a3dd98e19f122
Reviewed-on: https://go-review.googlesource.com/c/go/+/230797
Run-TryBot: Martin Möhrmann 
TryBot-Result: Gobot Gobot 
Reviewed-by: Robert Griesemer

strings: simpler and slightly faster implementation of FieldsFunc

2020-04-28T20:18:12+00:00

Removed the need for maintaining an extra variable in one of the inner loops,
leading to a slight speed-up for short strings.

Benchmarks run on a "quiet" MacBook Pro, 3.3GHz Dual-Core Intel Core i7,
with 16GB 2133MHz LPDDR3 RAM running macOS 10.15.4.

name                        old time/op    new time/op    delta
FieldsFunc/ASCII/16-4          147ns ± 0%     144ns ± 1%  -2.04%  (p=0.000 n=4+5)
FieldsFunc/ASCII/256-4        1.63µs ± 0%    1.59µs ± 1%  -2.50%  (p=0.008 n=5+5)
FieldsFunc/ASCII/4096-4       30.0µs ± 0%    29.3µs ± 2%    ~     (p=0.190 n=4+5)
FieldsFunc/ASCII/65536-4       491µs ± 5%     473µs ± 2%    ~     (p=0.095 n=5+5)
FieldsFunc/ASCII/1048576-4    8.02ms ± 7%    7.85ms ± 4%    ~     (p=0.548 n=5+5)
FieldsFunc/Mixed/16-4          182ns ± 1%     181ns ± 4%    ~     (p=0.357 n=5+5)
FieldsFunc/Mixed/256-4        1.74µs ± 1%    1.74µs ± 1%    ~     (p=0.881 n=5+5)
FieldsFunc/Mixed/4096-4       34.9µs ± 2%    34.7µs ± 0%    ~     (p=0.310 n=5+5)
FieldsFunc/Mixed/65536-4       595µs ± 1%     589µs ± 2%    ~     (p=0.095 n=5+5)
FieldsFunc/Mixed/1048576-4    10.1ms ± 3%     9.8ms ± 2%    ~     (p=0.095 n=5+5)

name                        old speed      new speed      delta
FieldsFunc/ASCII/16-4        109MB/s ± 1%   111MB/s ± 1%  +2.33%  (p=0.008 n=5+5)
FieldsFunc/ASCII/256-4       157MB/s ± 0%   161MB/s ± 1%  +2.57%  (p=0.008 n=5+5)
FieldsFunc/ASCII/4096-4      137MB/s ± 0%   140MB/s ± 2%    ~     (p=0.190 n=4+5)
FieldsFunc/ASCII/65536-4     134MB/s ± 4%   139MB/s ± 2%    ~     (p=0.095 n=5+5)
FieldsFunc/ASCII/1048576-4   131MB/s ± 6%   134MB/s ± 4%    ~     (p=0.548 n=5+5)
FieldsFunc/Mixed/16-4       87.8MB/s ± 1%  88.3MB/s ± 4%    ~     (p=0.421 n=5+5)
FieldsFunc/Mixed/256-4       147MB/s ± 1%   147MB/s ± 1%    ~     (p=0.841 n=5+5)
FieldsFunc/Mixed/4096-4      117MB/s ± 2%   118MB/s ± 0%    ~     (p=0.310 n=5+5)
FieldsFunc/Mixed/65536-4     110MB/s ± 1%   111MB/s ± 2%    ~     (p=0.095 n=5+5)
FieldsFunc/Mixed/1048576-4   104MB/s ± 3%   107MB/s ± 2%    ~     (p=0.095 n=5+5)

name                        old alloc/op   new alloc/op   delta
FieldsFunc/ASCII/16-4          32.0B ± 0%     32.0B ± 0%    ~     (all equal)
FieldsFunc/ASCII/256-4          352B ± 0%      352B ± 0%    ~     (all equal)
FieldsFunc/ASCII/4096-4       21.9kB ± 0%    21.9kB ± 0%    ~     (all equal)
FieldsFunc/ASCII/65536-4       448kB ± 0%     448kB ± 0%    ~     (all equal)
FieldsFunc/ASCII/1048576-4    8.85MB ± 0%    8.85MB ± 0%    ~     (p=0.738 n=5+5)
FieldsFunc/Mixed/16-4          48.0B ± 0%     48.0B ± 0%    ~     (all equal)
FieldsFunc/Mixed/256-4          416B ± 0%      416B ± 0%    ~     (all equal)
FieldsFunc/Mixed/4096-4       21.5kB ± 0%    21.5kB ± 0%    ~     (all equal)
FieldsFunc/Mixed/65536-4       448kB ± 0%     448kB ± 0%    ~     (all equal)
FieldsFunc/Mixed/1048576-4    8.85MB ± 0%    8.85MB ± 0%    ~     (p=0.690 n=5+5)

name                        old allocs/op  new allocs/op  delta
FieldsFunc/ASCII/16-4           1.00 ± 0%      1.00 ± 0%    ~     (all equal)
FieldsFunc/ASCII/256-4          1.00 ± 0%      1.00 ± 0%    ~     (all equal)
FieldsFunc/ASCII/4096-4         5.00 ± 0%      5.00 ± 0%    ~     (all equal)
FieldsFunc/ASCII/65536-4        12.0 ± 0%      12.0 ± 0%    ~     (all equal)
FieldsFunc/ASCII/1048576-4      24.0 ± 0%      24.0 ± 0%    ~     (all equal)
FieldsFunc/Mixed/16-4           1.00 ± 0%      1.00 ± 0%    ~     (all equal)
FieldsFunc/Mixed/256-4          1.00 ± 0%      1.00 ± 0%    ~     (all equal)
FieldsFunc/Mixed/4096-4         5.00 ± 0%      5.00 ± 0%    ~     (all equal)
FieldsFunc/Mixed/65536-4        12.0 ± 0%      12.0 ± 0%    ~     (all equal)
FieldsFunc/Mixed/1048576-4      24.0 ± 0%      24.0 ± 0%    ~     (all equal)

Change-Id: I06828d798ca1a624a26edd7f7b68c3bf2fc28f84
Reviewed-on: https://go-review.googlesource.com/c/go/+/229765
Reviewed-by: Martin Möhrmann

strings: remove an obsolete doc note for FieldsFunc

2020-04-23T22:10:10+00:00

Fixes #38630

Change-Id: I0b2b693dd88821dcfc035cf552b687565bb55ef6
GitHub-Last-Rev: 291b1b4dcf074860492bb67008f4e8228c655652
GitHub-Pull-Request: golang/go#38631
Reviewed-on: https://go-review.googlesource.com/c/go/+/229763
Reviewed-by: Robert Griesemer