Matrix Sum

mat_test.go

package main

import (
	"testing"
)

var (
	nRows, nCols = 10000, 27
	mat          [][]int
	n            = nRows * nCols
	// sum of algebraic series
	sum = n / 2 * (0 + (n - 1))
)

func init() {
	mat = make([][]int, nRows)
	for r := 0; r < nRows; r++ {
		row := make([]int, nCols)
		for c := 0; c < nCols; c++ {
			row[c] = r*nCols + c
		}
		mat[r] = row
	}
}

func sumByRows(m [][]int) int {
	total := 0
	for r := range m {
		for c := range m[0] {
			total += m[r][c]
		}
	}
	return total
}

func BenchmarkRows(b *testing.B) {
	for i := 0; i < b.N; i++ {
		s := sumByRows(mat)
		if s != sum {
			b.Fatalf("%v != %v", sum, s)
		}
	}
}

func sumByCols(m [][]int) int {
	total := 0
	for c := range m[0] {
		for r := range m {
			total += m[r][c]
		}
	}
	return total
}

func BenchmarkCols(b *testing.B) {
	for i := 0; i < b.N; i++ {
		s := sumByCols(mat)
		if s != sum {
			b.Fatalf("%v != %v", sum, s)
		}
	}
}