matrix.go

package main

import (
	"fmt"
	"math/rand"
	"os"
	"strconv"
	"runtime"
)

type Matrix [][]int

func computePart(i int, a, b, c *Matrix, ch chan int) {
	ac := len((*a)[0])
	bc := len((*b)[0])
	for j := 0; j < bc; j++ {
		part := 0
		for k := 0; k < ac; k++ {
			part += (*a)[i][k] * (*b)[k][j]
		}
		(*c)[i][j] = part
	}
	ch <- 1
}

func mulConcurrent(a, b *Matrix) Matrix {
	ar := len(*a)
	ac := len((*a)[0])
	br := len(*b)
	bc := len((*b)[0])
	if ac != br {
		panic("wrong matrix type")
	}
	c := make(Matrix, ar)
	for i := 0 ; i < ar ; i++ {
		c[i] = make([]int, bc)
	}

	ch := make(chan int)
	for i := 0 ; i < ar ; i++ {
		go computePart(i, a, b, &c, ch)
	}
	for i := 0 ; i < ar ; i++ {
		<- ch
	}
	return c
}


func mul(a, b *Matrix) Matrix {
	ar := len(*a)
	ac := len((*a)[0])
	br := len(*b)
	bc := len((*b)[0])
	if ac != br {
		panic("wrong matrix type")
	}
	c := make(Matrix, ar)
	for i := 0 ; i < ar ; i++ {
		c[i] = make([]int, bc)
		for j := 0 ; j < bc ; j++ {
			for k := 0 ; k < ac ; k++ {
				c[i][j] += (*a)[i][k] * (*b)[k][j]
			}
		}
	}
	return c
}


func main() {
	n, _ := strconv.Atoi(os.Args[1])
	k, _ := strconv.Atoi(os.Args[2])
	runtime.GOMAXPROCS(k)

	a := make(Matrix, n)
	b := make(Matrix, n)
	for i := 0 ; i < n ; i++ {
		a[i] = make([]int, n)
		b[i] = make([]int, n)
		for j := 0 ; j < n ; j++ {
			a[i][j] = rand.Intn(100)
			b[i][j] = rand.Intn(100)
		}
	}
	var c Matrix
	if k == 0 {
		c = mul(&a, &b)
	} else {
		c = mulConcurrent(&a, &b)
	}
	fmt.Println(c[0][0])
}