It’s as simple as:
var count = 1
var p = &count
func X() {
total :=0
for i:=0; i <1000000;i++ {
total = total + *p
}
}
no ?
> On Nov 30, 2018, at 11:48 AM, Mark Volkmann <r.mark.volkm...@gmail.com> wrote:
>
> I think I failed to come up with a good code example. But suppose I need to
> do something with a pointer inside a loop that really does require
> dereferencing it and the pointer never changes inside the loop. In that case
> will the Go compiler optimize that so the dereference doesn't happen in each
> loop iteration?
>
> On Fri, Nov 30, 2018 at 11:36 AM Jan Mercl <0xj...@gmail.com
> <mailto:0xj...@gmail.com>> wrote:
>
> On Fri, Nov 30, 2018 at 6:16 PM Mark Volkmann <r.mark.volkm...@gmail.com
> <mailto:r.mark.volkm...@gmail.com>> wrote:
>
> > Will the Go compiler optimize the pointer dereference so it doesn't happen
> > in every loop iteration? If not, is it common practice to do that outside
> > the loop like this?
> >
> > myValue := *myPtr
> > for _, v := range values {
> > fmt.Printf("%v %v\n", myValue, v)
> > }
>
> There's no pointer dereference inside the loop. But there's an allocation
> inside the loop, on every iteration, that puts a pointer to a copy of myValue
> into an interface{} that's passed to fmt.Printf. The allocation can be
> probably avoided:
>
> myValue := interface{}(*myPtr)
> for _, v := range values {
> fmt.Printf("%v %v\n", myValue, v)
> }
>
> But the %v verb handle pointers in many cases well. If that holds for the
> type of *myPtr then simply:
>
> for _, v := range values {
> fmt.Printf("%v %v\n", myPtr, v)
> }
>
> is what could be good enough.
>
> --
> -j
>
>
>
> --
> R. Mark Volkmann
> Object Computing, Inc.
>
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