From eeca44cd2727e648afbaa994f90ee37580d149f3 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Leandro=20L=C3=B3pez?= Date: Tue, 23 Mar 2021 14:14:59 -0300 Subject: [PATCH] Allocate resulting slice size instead of dynamically growing it MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We know for sure how big the resulting slice will be, so instead of having Go perform checks and reallocations whenever the slice grows too small by using `append` we calculate the resulting size earlier and directly index each element into the output slice. This result in only two allocations all the time, no matter how big the resulting slice will be. With it also come big performance improvements: name old time/op new time/op delta ToOrderedSlice/1_unique_identifiers-8 173ns ±10% 150ns ± 4% -13.16% (p=0.000 n=10+9) ToOrderedSlice/10_unique_identifiers-8 1.24µs ± 6% 0.51µs ± 5% -58.95% (p=0.000 n=9+9) ToOrderedSlice/100_unique_identifiers-8 20.4µs ±20% 4.0µs ± 5% -80.25% (p=0.000 n=10+9) ToOrderedSlice/1000_unique_identifiers-8 253µs ± 9% 40µs ± 5% -84.19% (p=0.000 n=10+10) ToOrderedSlice/10000_unique_identifiers-8 3.44ms ± 9% 0.37ms ± 5% -89.32% (p=0.000 n=9+9) ToOrderedSlice/100000_unique_identifiers-8 48.6ms ±13% 3.6ms ± 4% -92.49% (p=0.000 n=10+10) name old alloc/op new alloc/op delta ToOrderedSlice/1_unique_identifiers-8 40.0B ± 0% 40.0B ± 0% ~ (all equal) ToOrderedSlice/10_unique_identifiers-8 520B ± 0% 184B ± 0% -64.62% (p=0.000 n=10+10) ToOrderedSlice/100_unique_identifiers-8 4.10kB ± 0% 1.82kB ± 0% -55.75% (p=0.000 n=10+10) ToOrderedSlice/1000_unique_identifiers-8 32.8kB ± 0% 16.4kB ± 0% -49.95% (p=0.000 n=10+10) ToOrderedSlice/10000_unique_identifiers-8 826kB ± 0% 164kB ± 0% -80.16% (p=0.000 n=10+10) ToOrderedSlice/100000_unique_identifiers-8 9.25MB ± 0% 1.61MB ± 0% -82.64% (p=0.000 n=10+10) name old allocs/op new allocs/op delta ToOrderedSlice/1_unique_identifiers-8 2.00 ± 0% 2.00 ± 0% ~ (all equal) ToOrderedSlice/10_unique_identifiers-8 6.00 ± 0% 2.00 ± 0% -66.67% (p=0.000 n=10+10) ToOrderedSlice/100_unique_identifiers-8 9.00 ± 0% 2.00 ± 0% -77.78% (p=0.000 n=10+10) ToOrderedSlice/1000_unique_identifiers-8 12.0 ± 0% 2.0 ± 0% -83.33% (p=0.000 n=10+10) ToOrderedSlice/10000_unique_identifiers-8 21.0 ± 0% 2.0 ± 0% -90.48% (p=0.000 n=10+10) ToOrderedSlice/100000_unique_identifiers-8 31.0 ± 0% 2.0 ± 0% -93.55% (p=0.000 n=10+10) For ToSLice we use the same changes except the sort operation. In this case the results are even more impressive: allocations are stable at just 1 per operation, regardless of set size, and performance is orders of magnitude faster: name old time/op new time/op delta ToSlice/1_unique_identifiers-8 83.0ns ± 1% 92.4ns ± 0% +11.37% (p=0.000 n=9+8) ToSlice/10_unique_identifiers-8 295ns ± 4% 749ns ± 3% +154.21% (p=0.000 n=10+10) ToSlice/100_unique_identifiers-8 2.33µs ± 2% 4.28µs ± 2% +83.62% (p=0.000 n=9+8) ToSlice/1000_unique_identifiers-8 25.4µs ±10% 34.7µs ± 1% +36.51% (p=0.000 n=10+10) ToSlice/10000_unique_identifiers-8 215µs ± 2% 543µs ± 1% +152.15% (p=0.000 n=9+10) ToSlice/100000_unique_identifiers-8 2.05ms ± 2% 7.17ms ± 1% +249.53% (p=0.000 n=9+9) name old alloc/op new alloc/op delta ToSlice/1_unique_identifiers-8 16.0B ± 0% 16.0B ± 0% ~ (all equal) ToSlice/10_unique_identifiers-8 160B ± 0% 496B ± 0% +210.00% (p=0.000 n=10+10) ToSlice/100_unique_identifiers-8 1.79kB ± 0% 4.08kB ± 0% +127.68% (p=0.000 n=10+10) ToSlice/1000_unique_identifiers-8 16.4kB ± 0% 32.8kB ± 0% +99.90% (p=0.000 n=10+10) ToSlice/10000_unique_identifiers-8 164kB ± 0% 826kB ± 0% +404.12% (p=0.000 n=8+10) ToSlice/100000_unique_identifiers-8 1.61MB ± 0% 9.25MB ± 0% +475.93% (p=0.000 n=10+10) name old allocs/op new allocs/op delta ToSlice/1_unique_identifiers-8 1.00 ± 0% 1.00 ± 0% ~ (all equal) ToSlice/10_unique_identifiers-8 1.00 ± 0% 5.00 ± 0% +400.00% (p=0.000 n=10+10) ToSlice/100_unique_identifiers-8 1.00 ± 0% 8.00 ± 0% +700.00% (p=0.000 n=10+10) ToSlice/1000_unique_identifiers-8 1.00 ± 0% 11.00 ± 0% +1000.00% (p=0.000 n=10+10) ToSlice/10000_unique_identifiers-8 1.00 ± 0% 20.00 ± 0% +1900.00% (p=0.000 n=10+10) ToSlice/100000_unique_identifiers-8 1.00 ± 0% 30.00 ± 0% +2900.00% (p=0.000 n=10+10) Signed-off-by: Leandro López --- ast/identifier_set.go | 6 ++++-- ast/util.go | 6 ++++-- 2 files changed, 8 insertions(+), 4 deletions(-) diff --git a/ast/identifier_set.go b/ast/identifier_set.go index fe16bb2..c3066e6 100644 --- a/ast/identifier_set.go +++ b/ast/identifier_set.go @@ -22,9 +22,11 @@ func NewIdentifierSet(a ...Identifier) IdentifierSet { // ToSlice returns the elements of the current set as a slice func (set IdentifierSet) ToSlice() []Identifier { - var s []Identifier + s := make([]Identifier, len(set), len(set)) + j := 0 for v := range set { - s = append(s, v) + s[j] = v + j++ } return s } diff --git a/ast/util.go b/ast/util.go index e105a36..978c0fe 100644 --- a/ast/util.go +++ b/ast/util.go @@ -29,9 +29,11 @@ func (i IdentifierSet) AddIdentifiers(idents Identifiers) { // ToOrderedSlice returns the elements of the current set as an ordered slice. func (i IdentifierSet) ToOrderedSlice() []Identifier { - var s []Identifier + s := make([]Identifier, len(i), len(i)) + j := 0 for v := range i { - s = append(s, v) + s[j] = v + j++ } sort.Sort(identifierSorter(s)) return s