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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 <leandro.lopez@grafana.com>
47 lines
1.3 KiB
Go
47 lines
1.3 KiB
Go
/*
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Copyright 2016 Google Inc. All rights reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package ast
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import (
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"sort"
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)
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// AddIdentifiers adds a slice of identifiers to an identifier set.
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func (i IdentifierSet) AddIdentifiers(idents Identifiers) {
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for _, ident := range idents {
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i.Add(ident)
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}
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}
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// ToOrderedSlice returns the elements of the current set as an ordered slice.
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func (i IdentifierSet) ToOrderedSlice() []Identifier {
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s := make([]Identifier, len(i), len(i))
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j := 0
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for v := range i {
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s[j] = v
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j++
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}
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sort.Sort(identifierSorter(s))
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return s
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}
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type identifierSorter []Identifier
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func (s identifierSorter) Len() int { return len(s) }
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func (s identifierSorter) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
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func (s identifierSorter) Less(i, j int) bool { return s[i] < s[j] }
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