What does the GOMAXPROCS parameter mean in Go program execution settings?

The GOMAXPROCS parameter in Go defines the maximum number of operating system threads (OS threads) that the Go scheduler can use simultaneously to run goroutines. Simply put, this number indicates how many CPU cores can be utilized for parallel execution of code.

By default, GOMAXPROCS is set to the number of available logical processors on the machine. It can be changed using the runtime.GOMAXPROCS(n) function, where n is the desired number of threads.

Example:

package main

import (
    "fmt"
    "runtime"
)

func main() {
    fmt.Println("Current GOMAXPROCS value:", runtime.GOMAXPROCS(0))
    runtime.GOMAXPROCS(2) // limit to 2 threads
    fmt.Println("New GOMAXPROCS value:", runtime.GOMAXPROCS(0))
}

This is important for managing parallelism and program performance, especially on multi-processor systems.