Created
May 21, 2020 12:05
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concurrent calculation of factorial in golang
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package main | |
import ( | |
"fmt" | |
"math/big" | |
"runtime" | |
"time" | |
) | |
type computationRange struct { | |
start int64 | |
end int64 | |
} | |
var jobs []chan big.Int | |
var ranges chan []computationRange | |
func main() { | |
start := time.Now() | |
ranges = make(chan []computationRange) | |
go CalculateComputationRange(10000) | |
StartComputation() | |
result := CalculateFinalResult() | |
elapsed := time.Since(start) | |
fmt.Println("result: ", result) | |
fmt.Println("spent time in millis:", elapsed) | |
} | |
func CalculateComputationRange(factorialArgument int) { | |
var numberOfThreads int | |
if numberOfThreads = runtime.NumCPU(); factorialArgument < 20 { | |
numberOfThreads = 1 | |
} | |
var computationRangeSize = factorialArgument / numberOfThreads | |
computationRanges := make([]computationRange, numberOfThreads) | |
var nextComputationRangeEnd = int64(factorialArgument) | |
for i := numberOfThreads - 1; i >= 0; i-- { | |
computationRanges[i] = computationRange{ | |
start: 1 + nextComputationRangeEnd - int64(computationRangeSize), | |
end: nextComputationRangeEnd} | |
nextComputationRangeEnd = computationRanges[i].start - 1 | |
} | |
ranges <- computationRanges | |
} | |
func StartComputation() { | |
computationRanges := <-ranges | |
for i := 0; i < len(computationRanges); i++ { | |
job := make(chan big.Int, 1) | |
jobs = append(jobs, job) | |
go startRangeComputation(job, computationRanges[i], i) | |
} | |
} | |
func startRangeComputation(job chan<- big.Int, computationRange computationRange, rangeIndex int) { | |
product := big.NewInt(1) | |
for i := computationRange.start; i <= computationRange.end; i++ { | |
product.Mul(product, big.NewInt(i)) | |
} | |
job <- *product | |
} | |
func CalculateFinalResult() *big.Int { | |
result := big.NewInt(1) | |
for _, job := range jobs { | |
jobResult := <-job | |
close(job) | |
result.Mul(result, &jobResult) | |
} | |
return result | |
} |
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