using glide

vendor/github.com/templexxx/reedsolomon/mathtool/cntinverse.go

@@ -0,0 +1,193 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+)
+
+var vects = flag.Uint64("vects", 20, "number of vects (data+parity)")
+var data = flag.Uint64("data", 0, "number of data vects; keep it empty if you want to "+
+	"get the max num of inverse matrix")
+
+func init() {
+	flag.Usage = func() {
+		fmt.Printf("Usage of %s:\n", os.Args[0])
+		fmt.Println("  cntinverse [-flags]")
+		fmt.Println("  Valid flags:")
+		flag.PrintDefaults()
+	}
+}
+
+func main() {
+	flag.Parse()
+	if *vects > 256 {
+		fmt.Println("Error: vects must <= 256")
+		os.Exit(1)
+	}
+	if *data == 0 {
+		n := getMAXCCombination(*vects)
+		fmt.Println("max num of inverse matrix :", n)
+		os.Exit(0)
+	}
+	n := getCCombination(*vects, *data)
+	fmt.Println("num of inverse matrix:", n)
+	os.Exit(0)
+}
+
+func getMAXCCombination(a uint64) uint64 {
+	b := a / 2 // proved in mathtool/combination.jpg
+	return getCCombination(a, b)
+}
+
+func getCCombination(a, b uint64) uint64 {
+	top := make([]uint64, a-b)
+	bottom := make([]uint64, a-b-1)
+	for i := b + 1; i <= a; i++ {
+		top[i-b-1] = i
+	}
+	var i uint64
+	for i = 2; i <= a-b; i++ {
+		bottom[i-2] = i
+	}
+	for j := 0; j <= 5; j++ {
+		cleanEven(top, bottom)
+		clean3(top, bottom)
+		clean5(top, bottom)
+	}
+	cleanCoffeRound1(top, bottom)
+	if maxBottomBigger5more1(bottom) {
+		top = shuffTop(top)
+		cleanCoffeRound1(top, bottom)
+		cleanCoffeRound1(bottom, top)
+		cleanCoffeRound1(top, bottom)
+		cleanCoffeRound1(bottom, top)
+		cleanCoffeRound1(top, bottom)
+		cleanCoffeRound1(bottom, top)
+	}
+	var topV, bottomV uint64 = 1, 1
+	for _, t := range top {
+		topV = topV * t
+	}
+	for _, b := range bottom {
+		bottomV = bottomV * b
+	}
+	return topV / bottomV
+}
+
+func cleanEven(top, bottom []uint64) {
+	for i, b := range bottom {
+		if even(b) {
+			for j, t := range top {
+				if even(t) {
+					top[j] = t / 2
+					bottom[i] = b / 2
+					break
+				}
+			}
+		}
+	}
+}
+
+func even(a uint64) bool {
+	return a&1 == 0
+}
+
+func clean3(top, bottom []uint64) {
+	for i, b := range bottom {
+		if mod3(b) {
+			for j, t := range top {
+				if mod3(t) {
+					top[j] = t / 3
+					bottom[i] = b / 3
+					break
+				}
+			}
+		}
+	}
+}
+
+func mod3(a uint64) bool {
+	c := a / 3
+	if 3*c == a {
+		return true
+	}
+	return false
+}
+
+func clean5(top, bottom []uint64) {
+	for i, b := range bottom {
+		if mod5(b) {
+			for j, t := range top {
+				if mod5(t) {
+					top[j] = t / 5
+					bottom[i] = b / 5
+					break
+				}
+			}
+		}
+	}
+}
+
+func mod5(a uint64) bool {
+	c := a / 5
+	if 5*c == a {
+		return true
+	}
+	return false
+}
+
+func maxBottomBigger5more1(bottom []uint64) bool {
+	cnt := 0
+	for _, b := range bottom {
+		if b >= 5 {
+			cnt++
+		}
+	}
+	if cnt >= 2 {
+		return true
+	}
+	return false
+}
+
+func cleanCoffeRound1(top, bottom []uint64) {
+	for i, b := range bottom {
+		for j, t := range top {
+			if isCoffe(b, t) {
+				top[j] = t / b
+				bottom[i] = 1
+				break
+			}
+		}
+	}
+}
+
+func isCoffe(b, t uint64) bool {
+	c := t / b
+	if c*b == t {
+		return true
+	}
+	return false
+}
+
+func shuffTop(top []uint64) []uint64 {
+	var tmp uint64 = 1
+	newLen := len(top) + 1
+	for i, t := range top {
+		if t <= 5 {
+			tmp = tmp * t
+			newLen--
+			top[i] = 1
+		}
+	}
+	topNew := make([]uint64, newLen)
+	topNew[0] = tmp
+	cnt := 1
+	for _, t := range top {
+		if t != 1 {
+			topNew[cnt] = t
+			cnt++
+		}
+	}
+	return topNew
+}