go-jsonnet/ast/util.go
Leandro López eeca44cd27 Allocate resulting slice size instead of dynamically growing it
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>
2021-03-25 15:44:43 +01:00

47 lines
1.3 KiB
Go

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