Editing Thread pool (section)

== In languages ==
In [[Bash (Unix shell)|bash]] implemented by <code>--max-procs</code> / <code>-P</code> in [[xargs]], for example:
<syntaxhighlight lang="bash">
# Fetch 5 URLs in parallel
urls=(
    "https://example.com/file1.txt"
    "https://example.com/file2.txt"
    "https://example.com/file3.txt"
    "https://example.com/file4.txt"
    "https://example.com/file5.txt"
)

printf '%s\n' "${urls[@]}" | xargs -P 5 -I {} curl -sI {} | grep -i "content-length:"
</syntaxhighlight><ref>{{Cite web |last=Shved |first=Paul |date=2010-01-07 |title=Easy parallelization with Bash in Linux |url=http://coldattic.info/post/7/ |access-date=2025-01-26 |website=coldattic.info |language=en}}</ref><ref>{{Cite web |title=xargs(1) - Linux manual page |url=https://www.man7.org/linux/man-pages/man1/xargs.1.html |access-date=2025-01-26 |website=www.man7.org}}</ref><ref>{{Cite web |title=Controlling Parallelism (GNU Findutils 4.10.0) |url=https://www.gnu.org/software/findutils/manual/html_node/find_html/Controlling-Parallelism.html |access-date=2025-01-26 |website=www.gnu.org}}</ref>

In [[Go (programming language)|Go]], called worker pool:
<syntaxhighlight lang="go">
package main

import (
    "fmt"
    "time"
)

func worker(id int, jobs <-chan int, results chan<- int) {
    for j := range jobs {
        fmt.Println("worker", id, "started  job", j)
        time.Sleep(time.Second)
        fmt.Println("worker", id, "finished job", j)
        results <- j * 2
    }
}

func main() {
    const numJobs = 5
    jobs := make(chan int, numJobs)
    results := make(chan int, numJobs)

    for w := 1; w <= 3; w++ {
        go worker(w, jobs, results)
    }

    for j := 1; j <= numJobs; j++ {
        jobs <- j
    }
    close(jobs)

    for a := 1; a <= numJobs; a++ {
        <-results
    }
}
</syntaxhighlight>

It will print:
<syntaxhighlight lang="console">
$ time go run worker-pools.go 
worker 1 started  job 1
worker 2 started  job 2
worker 3 started  job 3
worker 1 finished job 1
worker 1 started  job 4
worker 2 finished job 2
worker 2 started  job 5
worker 3 finished job 3
worker 1 finished job 4
worker 2 finished job 5

real    0m2.358s
</syntaxhighlight><ref>{{Cite web |title=Go by Example: Worker Pools |url=https://gobyexample.com/worker-pools |access-date=2021-07-27 |website=gobyexample.com}}</ref><ref>{{Cite web |title=Effective Go - The Go Programming Language |url=https://golang.org/doc/effective_go#channels |access-date=2021-07-27 |website=golang.org |quote=another approach that manages resources well is to start a fixed number of handle goroutines all reading from the request channel. The number of goroutines limits the number of simultaneous calls to process}}</ref><ref>{{Cite web |title=The Case For A Go Worker Pool — brandur.org |url=https://brandur.org/go-worker-pool |access-date=2021-07-27 |website=brandur.org |quote=Worker pools are a model in which a fixed number of m workers (implemented in Go with goroutines) work their way through n tasks in a work queue (implemented in Go with a channel). Work stays in a queue until a worker finishes up its current task and pulls a new one off.}}</ref>