Go atom .AddFloat32 ()

Question

I need a function to atomically add float32 values ​​in Go. Here's what happened based on some C code I found:

package atomic import ( "sync/atomic" "unsafe" "math" ) func AddFloat32(addr *float32, delta float32) (new float32) { unsafeAddr := (*uint32)(unsafe.Pointer(addr)) for { oldValue := math.Float32bits(*addr) new = *addr + delta newValue := math.Float32bits(new) if atomic.CompareAndSwapUint32(unsafeAddr, oldValue, newValue) { return } } } 

Should it work (i.e. really be atomic)? Is there a better way to do this in Go?

Answer 1

Look for some code from the Go standard library for customization. For example, from go/src/sync/atomic/64bit_arm.go ,

 func addUint64(val *uint64, delta uint64) (new uint64) { for { old := *val new = old + delta if CompareAndSwapUint64(val, old, new) { break } } return } 

For float32 that becomes,

 package main import ( "fmt" "math" "sync/atomic" "unsafe" ) func AddFloat32(val *float32, delta float32) (new float32) { for { old := *val new = old + delta if atomic.CompareAndSwapUint32( (*uint32)(unsafe.Pointer(val)), math.Float32bits(old), math.Float32bits(new), ) { break } } return } func main() { val, delta := float32(math.Pi), float32(math.E) fmt.Println(val, delta, val+delta) new := AddFloat32(&val, delta) fmt.Println(val, new) } 

Conclusion:

  3.1415927 2.7182817 5.8598747
 5.8598747 5.8598747