The step method implementations check directly if the next rune
only needs one byte to be decoded and avoid calling utf8.DecodeRune
for such ASCII characters.
Introduce the same fast path optimization for rune decoding
for the context methods.
Results for regexp benchmarks that use the context methods:
name old time/op new time/op delta
AnchoredLiteralShortNonMatch-4 97.5ns ± 1% 94.8ns ± 2% -2.80% (p=0.000 n=45+43)
AnchoredShortMatch-4 163ns ± 1% 160ns ± 1% -1.84% (p=0.000 n=46+47)
NotOnePassShortA-4 742ns ± 2% 742ns ± 2% ~ (p=0.440 n=49+50)
NotOnePassShortB-4 535ns ± 1% 533ns ± 2% -0.37% (p=0.005 n=46+48)
OnePassLongPrefix-4 169ns ± 2% 166ns ± 2% -2.06% (p=0.000 n=50+49)
Change-Id: Ib302d9e8c63333f02695369fcf9963974362e335
Reviewed-on: https://go-review.googlesource.com/38256
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This change removes a lot of dead code. Some of the code has never been
used, not even when it was first commited. The rest shouldn't have
survived refactors.
This change doesn't remove unused routines helpful for debugging, nor
does it remove code that's used in commented out blocks of code that are
only unused temporarily. Furthermore, unused constants weren't removed
when they were part of a set of constants from specifications.
One noteworthy omission from this CL are about 1000 lines of unused code
in cmd/fix, 700 lines of which are the typechecker, which hasn't been
used ever since the pre-Go 1 fixes have been removed. I wasn't sure if
this code should stick around for future uses of cmd/fix or be culled as
well.
Change-Id: Ib714bc7e487edc11ad23ba1c3222d1fd02e4a549
Reviewed-on: https://go-review.googlesource.com/20926
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
There's nothing guaranteeing that the *Regexp isn't in active use,
and so copying the sync.Mutex value is invalid.
Updates #14839.
Change-Id: Iddf52bf69df1b563377922399f64a571f76b95dd
Reviewed-on: https://go-review.googlesource.com/20841
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>
The tree's pretty inconsistent about single space vs double space
after a period in documentation. Make it consistently a single space,
per earlier decisions. This means contributors won't be confused by
misleading precedence.
This CL doesn't use go/doc to parse. It only addresses // comments.
It was generated with:
$ perl -i -npe 's,^(\s*// .+[a-z]\.) +([A-Z]),$1 $2,' $(git grep -l -E '^\s*//(.+\.) +([A-Z])')
$ go test go/doc -update
Change-Id: Iccdb99c37c797ef1f804a94b22ba5ee4b500c4f7
Reviewed-on: https://go-review.googlesource.com/20022
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Dave Day <djd@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This helps users who wish to use separate Regexps in each goroutine to
avoid lock contention. Previously they had to parse the expression
multiple times to achieve this.
I used variants of the included benchmark to evaluate this change. I
used the arguments -benchtime 20s -cpu 1,2,4,8,16 on a machine with 16
hardware cores.
Comparing a single shared Regexp vs. copied Regexps, we can see that
lock contention causes huge slowdowns at higher levels of parallelism.
The copied version shows the expected linear speedup.
name old time/op new time/op delta
MatchParallel 366ns ± 0% 370ns ± 0% +1.09% (p=0.000 n=10+8)
MatchParallel-2 324ns ±28% 184ns ± 1% -43.37% (p=0.000 n=10+10)
MatchParallel-4 352ns ± 5% 93ns ± 1% -73.70% (p=0.000 n=9+10)
MatchParallel-8 480ns ± 3% 46ns ± 0% -90.33% (p=0.000 n=9+8)
MatchParallel-16 510ns ± 8% 24ns ± 6% -95.36% (p=0.000 n=10+8)
I also compared a modified version of Regexp that has no mutex and a
single machine (the "RegexpForSingleGoroutine" rsc mentioned in
https://github.com/golang/go/issues/8232#issuecomment-66096128).
In this next test, I compared using N copied Regexps vs. N separate
RegexpForSingleGoroutines. This shows that, even for this relatively
simple regex, avoiding the lock entirely would only buy about 10-12%
further improvement.
name old time/op new time/op delta
MatchParallel 370ns ± 0% 322ns ± 0% -12.97% (p=0.000 n=8+8)
MatchParallel-2 184ns ± 1% 162ns ± 1% -11.60% (p=0.000 n=10+10)
MatchParallel-4 92.7ns ± 1% 81.1ns ± 2% -12.43% (p=0.000 n=10+10)
MatchParallel-8 46.4ns ± 0% 41.8ns ±10% -9.78% (p=0.000 n=8+10)
MatchParallel-16 23.7ns ± 6% 20.6ns ± 1% -13.14% (p=0.000 n=8+8)
Updates #8232.
Change-Id: I15201a080c363d1b44104eafed46d8df5e311902
Reviewed-on: https://go-review.googlesource.com/16110
Reviewed-by: Russ Cox <rsc@golang.org>
Regular expressions involving a (x){0} term are
simplified by removing this term from the
expression, just before the expression is compiled.
The number of subexpressions is evaluated before
the simplification. The number of capture instructions
in the compiled expressions is not necessarily in line
with the number of subexpressions.
When the ReplaceAll(String) methods are used, a number
of capture slots (nmatch) is evaluated as 2*(s+1)
(s being the number of subexpressions).
In some case, it can be higher than the number of capture
instructions evaluated at compile time, resulting in a
panic when the internal slices of regexp.machine
are resized to this value.
Fixed by capping the number of capture slots to the number
of capture instructions.
I must say I do not really see the benefits of setting
nmatch lower than re.prog.NumCap using this 2*(s+1) formula,
so perhaps this can be further simplified.
Fixes#11178Fixes#11176
Change-Id: I21415e8ef2dd5f2721218e9a679f7f6bfb76ae9b
Reviewed-on: https://go-review.googlesource.com/14013
Reviewed-by: Russ Cox <rsc@golang.org>
In 1.6, go doc is more likely to be available.
Change-Id: I970ad1d3317b35273f5c8d830f75713d3570c473
Reviewed-on: https://go-review.googlesource.com/10518
Reviewed-by: Andrew Gerrand <adg@golang.org>
