forked from EddieRingle/genprime
/
genprime.go
83 lines (77 loc) · 1.6 KB
/
genprime.go
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package main
import ("fmt"; "os"; "math"; "strconv")
func getTime() float64 {
sec, nsec, err := os.Time();
var time float64 = 0;
if err == nil {
time = float64(sec) + (float64(nsec) * math.Pow10(-9));
}
return time;
}
func isprime(x int) int {
if x < 2 {
return 0;
}
if x < 4 {
return 1;
}
if x == 5 {
return 1;
}
if x % 2 == 0 {
return 0;
}
if x % 5 == 0 {
return 0;
}
if (x + 1) % 6 != 0 {
if (x - 1) % 6 != 0 {
return 0;
}
}
match := 0;
lim := math.Sqrt(float64(x)) + 1.0;
for y := 3; float64(y) < lim; y += 2 {
if x % y == 0 {
match = 1;
break;
}
}
if match == 1 {
return 0;
}
return 1;
}
func genprime(max int) int {
current := 1;
for count := 0; count < max; current++ {
if isprime(current) == 1 {
count++;
}
}
return (current - 1);
}
func main() {
var err os.Error = nil;
var start int = 0;
var stop int = 0;
if len(os.Args) > 1 {
start, err = strconv.Atoi(os.Args[1]);
if err != nil {
os.Exit(1);
}
}
if len(os.Args) > 2 {
stop, err = strconv.Atoi(os.Args[2]);
if err != nil {
os.Exit(2);
}
}
for x := start; x <= stop; x += start {
begin := getTime();
last := genprime(x);
end := getTime();
var duration float64 = (end - begin);
fmt.Printf("Found %8d primes in %10f seconds (last was %8d)\n", x, duration, last)
}
}