I found this performance difference by benchmarking the two:
func IntAdd(words [][]byte) map[string]int {
var m = make(map[string]int)
for _, w := range words {
m[string(w)] = m[string(w)] + 1
}
return m
}
func IntIncrement(words [][]byte) map[string]int {
var m = make(map[string]int)
for _, w := range words {
m[string(w)]++
}
return m
}
IntAdd is obviously slower than IntIncrement.
On Wednesday, March 17, 2021 at 4:22:53 PM UTC-4 [email protected]
wrote:
> Hi,
>
> have you verified this using a disassembler or benchmarks? Just asking
> because this is, as far as I'm concerned, a job for the compiler, to
> eliminate the overhead automatically - and I could well imagine that it's
> already doing it. There definitely shouldn't be a new language construct
> for this.
>
> On Wed, Mar 17, 2021 at 9:19 PM [email protected] <[email protected]>
> wrote:
>
>> Now, to modify a map element, especially the element type is not a basic
>> type, two hashes are needed to compute. This is often unnecessary and
>> inefficient. For example:
>>
>> package main
>>
>> type T struct{
>> N int
>> // ... more fields
>> }
>>
>> func main() {
>> var m = map[string]T{}
>> m["foo"] = T{N: 0}
>>
>> // modify
>> t := m["foo"] // first hashing
>> t.N++
>> m["foo"] = t // second hashing
>> }
>>
>> Will it be good to add a new builtin function, modify(m Map[Key]Value, k
>> Key, func(v *Value)), to modify map elements with only one hash? A use
>> example:
>>
>> package main
>>
>> type T struct{
>> N int
>> // ... more fields
>> }
>>
>> func main() {
>> var m = map[string]T{}
>> m["foo"] = T{N: 0}
>>
>> // modify
>> modify(m. "foo", func(t *T) {
>> t.N++
>> })
>> }
>>
>> --
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>> .
>>
>
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