How should I choose threshold for parallel.Range?
Running:
package main
import (
"fmt"
"log"
"runtime"
"sync"
"github.com/ExaScience/pargo/parallel"
)
func main() {
log.SetFlags(log.Lshortfile)
fmt.Println("GOMAXPROCS", runtime.GOMAXPROCS(0))
total := 1000000
run(total)
run(total - 1)
}
func run(total int) {
fmt.Println("total:", total)
for threshold := -5; threshold < 6; threshold++ {
mu := &sync.Mutex{}
count := 0
parallel.Range(0, total, threshold, func(low, high int) {
mu.Lock()
defer mu.Unlock()
count++
})
fmt.Printf("threshold\t%v\tcount\t%v\n", threshold, count)
}
}
produces:
GOMAXPROCS 2
total: 1000000
threshold -5 count 262144
threshold -4 count 262144
threshold -3 count 475712
threshold -2 count 524288
threshold -1 count 1000000
threshold 0 count 1000000
threshold 1 count 2
threshold 2 count 4
threshold 3 count 8
threshold 4 count 8
threshold 5 count 16
total: 999999
threshold -5 count 262144
threshold -4 count 262144
threshold -3 count 475711
threshold -2 count 524288
threshold -1 count 999999
threshold 0 count 999999
threshold 1 count 3
threshold 2 count 7
threshold 3 count 8
threshold 4 count 15
threshold 5 count 16
I don’t understand what it is intended to do.