85 lines
1.8 KiB
Go
85 lines
1.8 KiB
Go
package main
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//
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// a MapReduce pseudo-application to test that workers
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// execute reduce tasks in parallel.
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//
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// go build -buildmode=plugin rtiming.go
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//
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import "6.5840/mr"
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import "fmt"
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import "os"
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import "syscall"
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import "time"
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import "io/ioutil"
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func nparallel(phase string) int {
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// create a file so that other workers will see that
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// we're running at the same time as them.
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pid := os.Getpid()
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myfilename := fmt.Sprintf("mr-worker-%s-%d", phase, pid)
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err := ioutil.WriteFile(myfilename, []byte("x"), 0666)
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if err != nil {
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panic(err)
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}
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// are any other workers running?
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// find their PIDs by scanning directory for mr-worker-XXX files.
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dd, err := os.Open(".")
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if err != nil {
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panic(err)
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}
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names, err := dd.Readdirnames(1000000)
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if err != nil {
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panic(err)
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}
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ret := 0
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for _, name := range names {
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var xpid int
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pat := fmt.Sprintf("mr-worker-%s-%%d", phase)
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n, err := fmt.Sscanf(name, pat, &xpid)
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if n == 1 && err == nil {
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err := syscall.Kill(xpid, 0)
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if err == nil {
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// if err == nil, xpid is alive.
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ret += 1
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}
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}
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}
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dd.Close()
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time.Sleep(1 * time.Second)
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err = os.Remove(myfilename)
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if err != nil {
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panic(err)
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}
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return ret
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}
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func Map(filename string, contents string) []mr.KeyValue {
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kva := []mr.KeyValue{}
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kva = append(kva, mr.KeyValue{"a", "1"})
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kva = append(kva, mr.KeyValue{"b", "1"})
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kva = append(kva, mr.KeyValue{"c", "1"})
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kva = append(kva, mr.KeyValue{"d", "1"})
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kva = append(kva, mr.KeyValue{"e", "1"})
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kva = append(kva, mr.KeyValue{"f", "1"})
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kva = append(kva, mr.KeyValue{"g", "1"})
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kva = append(kva, mr.KeyValue{"h", "1"})
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kva = append(kva, mr.KeyValue{"i", "1"})
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kva = append(kva, mr.KeyValue{"j", "1"})
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return kva
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}
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func Reduce(key string, values []string) string {
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n := nparallel("reduce")
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val := fmt.Sprintf("%d", n)
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return val
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}
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