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package imaging
import (
"runtime"
"sync"
"sync/atomic"
)
// parallel starts parallel image processing based on the current GOMAXPROCS value.
// If GOMAXPROCS = 1 it uses no parallelization.
// If GOMAXPROCS > 1 it spawns N=GOMAXPROCS workers in separate goroutines.
func parallel(dataSize int, fn func(partStart, partEnd int)) {
numGoroutines := 1
partSize := dataSize
numProcs := runtime.GOMAXPROCS(0)
if numProcs > 1 {
numGoroutines = numProcs
partSize = dataSize / (numGoroutines * 10)
if partSize < 1 {
partSize = 1
}
}
if numGoroutines == 1 {
fn(0, dataSize)
} else {
var wg sync.WaitGroup
wg.Add(numGoroutines)
idx := uint64(0)
for p := 0; p < numGoroutines; p++ {
go func() {
defer wg.Done()
for {
partStart := int(atomic.AddUint64(&idx, uint64(partSize))) - partSize
if partStart >= dataSize {
break
}
partEnd := partStart + partSize
if partEnd > dataSize {
partEnd = dataSize
}
fn(partStart, partEnd)
}
}()
}
wg.Wait()
}
}
// absint returns the absolute value of i.
func absint(i int) int {
if i < 0 {
return -i
}
return i
}
// clamp rounds and clamps float64 value to fit into uint8.
func clamp(x float64) uint8 {
v := int64(x + 0.5)
if v > 255 {
return 255
}
if v > 0 {
return uint8(v)
}
return 0
}
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