mirror of https://github.com/golang/go.git
d8b7bd6a1f
This encoding algorithm, which prioritizes speed over output size, is
based on Snappy's LZ77-style encoder: github.com/golang/snappy
This commit keeps the diff between this package's encodeBestSpeed
function and and Snappy's encodeBlock function as small as possible (see
the diff below). Follow-up commits will improve this package's
performance and output size.
This package's speed benchmarks:
name old speed new speed delta
EncodeDigitsSpeed1e4-8 40.7MB/s ± 0% 73.0MB/s ± 0% +79.18% (p=0.008 n=5+5)
EncodeDigitsSpeed1e5-8 33.0MB/s ± 0% 77.3MB/s ± 1% +134.04% (p=0.008 n=5+5)
EncodeDigitsSpeed1e6-8 32.1MB/s ± 0% 82.1MB/s ± 0% +156.18% (p=0.008 n=5+5)
EncodeTwainSpeed1e4-8 42.1MB/s ± 0% 65.0MB/s ± 0% +54.61% (p=0.008 n=5+5)
EncodeTwainSpeed1e5-8 46.3MB/s ± 0% 80.0MB/s ± 0% +72.81% (p=0.008 n=5+5)
EncodeTwainSpeed1e6-8 47.3MB/s ± 0% 81.7MB/s ± 0% +72.86% (p=0.008 n=5+5)
Here's the milliseconds taken, before and after this commit, to compress
a number of test files:
Go's src/compress/testdata files:
4 1 e.txt
8 4 Mark.Twain-Tom.Sawyer.txt
github.com/golang/snappy's benchmark files:
3 1 alice29.txt
12 3 asyoulik.txt
6 1 fireworks.jpeg
1 1 geo.protodata
1 0 html
2 2 html_x_4
6 3 kppkn.gtb
11 4 lcet10.txt
5 1 paper-100k.pdf
14 6 plrabn12.txt
17 6 urls.10K
Larger files linked to from
https://docs.google.com/spreadsheets/d/1VLxi-ac0BAtf735HyH3c1xRulbkYYUkFecKdLPH7NIQ/edit#gid=166102500
2409 3182 adresser.001
16757 11027 enwik9
13764 12946 gob-stream
153978 74317 rawstudio-mint14.tar
4371 770 sharnd.out
Output size is larger. In the table below, the first column is the input
size, the second column is the output size prior to this commit, the
third column is the output size after this commit.
100003 47707 50006 e.txt
387851 172707 182930 Mark.Twain-Tom.Sawyer.txt
152089 62457 66705 alice29.txt
125179 54503 57274 asyoulik.txt
123093 122827 123108 fireworks.jpeg
118588 18574 20558 geo.protodata
102400 16601 17305 html
409600 65506 70313 html_x_4
184320 49007 50944 kppkn.gtb
426754 166957 179355 lcet10.txt
102400 82126 84937 paper-100k.pdf
481861 218617 231988 plrabn12.txt
702087 241774 258020 urls.10K
1073741824 43074110 57269781 adresser.001
1000000000 365772256 391052000 enwik9
1911399616 340364558 378679516 gob-stream
8558382592 3807229562 3972329193 rawstudio-mint14.tar
200000000 200061040 200015265 sharnd.out
The diff between github.com/golang/snappy's encodeBlock function and
this commit's encodeBestSpeed function:
1c1,7
< func encodeBlock(dst, src []byte) (d int) {
---
> func encodeBestSpeed(dst []token, src []byte) []token {
> // This check isn't in the Snappy implementation, but there, the caller
> // instead of the callee handles this case.
> if len(src) < minNonLiteralBlockSize {
> return emitLiteral(dst, src)
> }
>
4c10
< // and len(src) <= maxBlockSize and maxBlockSize == 65536.
---
> // and len(src) <= maxStoreBlockSize and maxStoreBlockSize == 65535.
65c71
< if load32(src, s) == load32(src, candidate) {
---
> if s-candidate < maxOffset && load32(src, s) == load32(src, candidate) {
73c79
< d += emitLiteral(dst[d:], src[nextEmit:s])
---
> dst = emitLiteral(dst, src[nextEmit:s])
90c96
< // This is an inlined version of:
---
> // This is an inlined version of Snappy's:
93c99,103
< for i := candidate + 4; s < len(src) && src[i] == src[s]; i, s = i+1, s+1 {
---
> s1 := base + maxMatchLength
> if s1 > len(src) {
> s1 = len(src)
> }
> for i := candidate + 4; s < s1 && src[i] == src[s]; i, s = i+1, s+1 {
96c106,107
< d += emitCopy(dst[d:], base-candidate, s-base)
---
> // matchToken is flate's equivalent of Snappy's emitCopy.
> dst = append(dst, matchToken(uint32(s-base-3), uint32(base-candidate-minOffsetSize)))
114c125
< if uint32(x>>8) != load32(src, candidate) {
---
> if s-candidate >= maxOffset || uint32(x>>8) != load32(src, candidate) {
124c135
< d += emitLiteral(dst[d:], src[nextEmit:])
---
> dst = emitLiteral(dst, src[nextEmit:])
126c137
< return d
---
> return dst
This change is based on https://go-review.googlesource.com/#/c/21021/ by
Klaus Post, but it is a separate changelist as cl/21021 seems to have
stalled in code review, and the Go 1.7 feature freeze approaches.
Golang-dev discussion:
https://groups.google.com/d/topic/golang-dev/XYgHX9p8IOk/discussion and
of course cl/21021.
Change-Id: Ib662439417b3bd0b61c2977c12c658db3e44d164
Reviewed-on: https://go-review.googlesource.com/22370
Reviewed-by: Russ Cox <rsc@golang.org>
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|---|---|---|
| .github | ||
| api | ||
| doc | ||
| lib/time | ||
| misc | ||
| src | ||
| test | ||
| .gitattributes | ||
| .gitignore | ||
| AUTHORS | ||
| CONTRIBUTING.md | ||
| CONTRIBUTORS | ||
| LICENSE | ||
| PATENTS | ||
| README.md | ||
| favicon.ico | ||
| robots.txt | ||
README.md
The Go Programming Language
Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.
For documentation about how to install and use Go, visit https://golang.org/ or load doc/install-source.html in your web browser.
Our canonical Git repository is located at https://go.googlesource.com/go. There is a mirror of the repository at https://github.com/golang/go.
Go is the work of hundreds of contributors. We appreciate your help!
To contribute, please read the contribution guidelines: https://golang.org/doc/contribute.html
Note that we do not accept pull requests and that we use the issue tracker for bug reports and proposals only. Please ask questions on https://forum.golangbridge.org or https://groups.google.com/forum/#!forum/golang-nuts.
Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.
--
Binary Distribution Notes
If you have just untarred a binary Go distribution, you need to set the environment variable $GOROOT to the full path of the go directory (the one containing this file). You can omit the variable if you unpack it into /usr/local/go, or if you rebuild from sources by running all.bash (see doc/install-source.html). You should also add the Go binary directory $GOROOT/bin to your shell's path.
For example, if you extracted the tar file into $HOME/go, you might put the following in your .profile:
export GOROOT=$HOME/go
export PATH=$PATH:$GOROOT/bin
See https://golang.org/doc/install or doc/install.html for more details.