@Jan Thank you for the feedback. I will try with a higher number of
constants. By the way, my benchmark tries all the path:
func BenchmarkStringerWithSwitch(b *testing.B) {
for i := 0; i < b.N ; i++ {
p := Pill(i%20)
_ = p.String()
}
}
> I can't find any compile time check in your code
I did not add it since it was not the original question ^^
But why can't we have the check and a switch?
Here is the code:
package main
import "strconv"
func _() {
// An "invalid array index" compiler error signifies that the constant
values have changed.
// Re-run the stringer command to generate them again.
var x [1]struct{}
_ = x[Placebo-0]
_ = x[Aspirin-1]
_ = x[Ibuprofen-2]
}
func (i Pill) String() string {
switch i {
case 0: return "Placebo"
case 1: return "Aspirin"
case 2: return "Ibuprofen"
case 3: return "Paracetamol"
default: return "Pill(" + strconv.FormatInt(int64(i), 10) + ")"
}
}
Le mardi 18 février 2020 14:06:14 UTC+4, Jan Mercl a écrit :
>
> On Tue, Feb 18, 2020 at 10:37 AM Vincent Blanchon
> <blancho...@gmail.com <javascript:>> wrote:
>
> > @Jan, yes definitely. By the way, here are some numbers from a benchmark
> I made with 20 constants:
> >
> > name time/op
> > Stringer-4 4.16ns ± 2%
> >
> > StringerWithSwitch-4 3.81ns ± 1%
> >
> > StringerWithMap-4 28.60ns ± 2%
>
> 20 is a small number. In general, measuring things where one iteration
> is in single digit nanoseconds can be misleading as discussed earlier.
> The probably most important thing is how a chosen implementation
> scales. To measure that, I suggest to make the number of the constants
> in hundreds, if not thousands and having the loop exercise all the
> paths, so the branch predictor cannot learn a single, happy one. In
> any case, it's much safer to shift the time/op to at least
> microseconds, otherwise the overhead of the test per se becomes
> comparable to the measured thing and it just adds noise at minimum.
>
> > @Pierre, the compilation check can also be done if we do not have a
> slice. In my example with the switch, I still kept the compilation check.
>
> I can't find any compile time check in your code (the one using the
> switch) that can detect a constant has changed its value since
> stringer was run.
>
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