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strings: Index(s, "x") not as optimized as bytes.IndexByte #3751

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bradfitz opened this issue Jun 18, 2012 · 19 comments
Closed

strings: Index(s, "x") not as optimized as bytes.IndexByte #3751

bradfitz opened this issue Jun 18, 2012 · 19 comments
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FrozenDueToAge Performance
Milestone
Go1.2

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@bradfitz
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bytes.IndexByte is implemented in assembly:

http://golang.org/pkg/bytes/#IndexByte

The strings package lacks an IndexByte method.  It does have a special case for Index
when len(sep) == 1, but not in assembly:

http://golang.org/src/pkg/strings/strings.go?s=1834:1863#L71

Low priority, but inconsistent. I noticed a couple weeks ago when I was looking at some
profiles.
@robpike
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robpike commented Jun 18, 2012

Comment 1:

Status changed to Accepted.

@rsc
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rsc commented Sep 12, 2012

Comment 2:

Labels changed: added go1.1.

@rsc
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rsc commented Dec 10, 2012

Comment 3:

Labels changed: added size-l.

@bradfitz
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Comment 4:

Also:
runtime.eqstring doesn't use the assembly from bytes/asm_amd64.s

@adg
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adg commented Feb 13, 2013

Comment 5:

What's the best approach here? Copy the code from bytes, or use unsafe tricks to convert
the string to a []byte and defer to bytes.IndexByte?

@bradfitz
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Comment 6:

Russ was proposing moving some of this shared code into package runtime, and having
bytes, strings, and the runtime use it.

@alberts
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alberts commented Feb 13, 2013

Comment 7:

On the runtime.eqstring topic: I've been dealing with database type app that scans
through lots of strings doing equality comparisons, where depending on some details, the
variability in the string is known to be at the start or at the end.
I believe it would have been very useful to have something like
strings.Equal(s1, s2 string, reverse bool) bool
that calls into some suitable assembler somewhere.
Could probably roll our own, but this seems close to the kind of thing the runtime
should be good at.

@bradfitz
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Comment 8:

That's a pretty gross API for the strings package, or the runtime package.

@rsc
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rsc commented Feb 13, 2013

Comment 9:

Please do not send CLs for this issue. I will take care of it later.

@rsc
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rsc commented Mar 12, 2013

Comment 10:

Labels changed: added go1.1maybe, removed go1.1.

@randall77
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Comment 12:

This issue was updated by revision 3d5daa2.

R=bradfitz, r, khr, dave, remyoudompheng, fullung, minux.ma, ality
CC=golang-dev
https://golang.org/cl/8056043

@bradfitz
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bradfitz commented Apr 3, 2013

Comment 13:

Labels changed: added optimization.

@bradfitz
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bradfitz commented Apr 3, 2013

Comment 14:

Labels changed: added performance.

@bradfitz
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bradfitz commented Apr 3, 2013

Comment 15:

Labels changed: removed optimization.

@bradfitz
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Comment 16:

I opened a related issue #5354 for bytes.Compare.

@robpike
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robpike commented May 18, 2013

Comment 17:

Labels changed: added go1.2maybe, removed go1.1maybe.

@rsc
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rsc commented Jul 30, 2013

Comment 18:

Labels changed: added feature.

@bradfitz
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bradfitz commented Aug 1, 2013

Comment 19:

This issue was updated by revision e2a1bd6.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/12289043

@bradfitz
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bradfitz commented Aug 5, 2013

Comment 20:

This issue was closed by revision 598c789.

Status changed to Fixed.

@rsc rsc added this to the Go1.2 milestone Apr 14, 2015
@rsc rsc removed the go1.2maybe label Apr 14, 2015
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@bradfitz @rsc @alberts @robpike @randall77 @adg @gopherbot