Finding all prime numbers within a range
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I am trying to find all primes less than 2,000,000 and sum them together. My code currently takes 1'36" to run. Is there a faster way to get my solution?
The logic I am following in this code is make a list of all primes I have found. Then check that every odd number less than 2,000,000 is not divisible by any of the primes in my list. If that is the case I am calling the number prime.
package main
import ("fmt"
"time"
)
func find_primes(max int) int {
// list of all primes that we find
var primes int
primes = append(primes, 2)
var is_prime = true
for i:=3; i<=max; i++ {
is_prime = false
// only odds can be prime
if i%2 != 0 {
is_prime = true
// should not be divisible by any previous
// prime numbers
for _, x := range primes {
if i%x == 0 {
is_prime = false
break
}
}
}
if is_prime {
primes = append(primes, i)
}
}
return primes
}
// just sume up all of the primes
func sum_primes(primes int) int {
var total int = 0
for _, x := range primes {
total = total + x
}
return total
}
func main() {
start := time.Now()
// find all primes less than 2,000,000
primes := find_primes(2000000)
sum := sum_primes(primes)
fmt.Println(sum)
t := time.Now()
elapsed := t.Sub(start)
fmt.Println(elapsed)
}
go
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add a comment |
$begingroup$
I am trying to find all primes less than 2,000,000 and sum them together. My code currently takes 1'36" to run. Is there a faster way to get my solution?
The logic I am following in this code is make a list of all primes I have found. Then check that every odd number less than 2,000,000 is not divisible by any of the primes in my list. If that is the case I am calling the number prime.
package main
import ("fmt"
"time"
)
func find_primes(max int) int {
// list of all primes that we find
var primes int
primes = append(primes, 2)
var is_prime = true
for i:=3; i<=max; i++ {
is_prime = false
// only odds can be prime
if i%2 != 0 {
is_prime = true
// should not be divisible by any previous
// prime numbers
for _, x := range primes {
if i%x == 0 {
is_prime = false
break
}
}
}
if is_prime {
primes = append(primes, i)
}
}
return primes
}
// just sume up all of the primes
func sum_primes(primes int) int {
var total int = 0
for _, x := range primes {
total = total + x
}
return total
}
func main() {
start := time.Now()
// find all primes less than 2,000,000
primes := find_primes(2000000)
sum := sum_primes(primes)
fmt.Println(sum)
t := time.Now()
elapsed := t.Sub(start)
fmt.Println(elapsed)
}
go
$endgroup$
add a comment |
$begingroup$
I am trying to find all primes less than 2,000,000 and sum them together. My code currently takes 1'36" to run. Is there a faster way to get my solution?
The logic I am following in this code is make a list of all primes I have found. Then check that every odd number less than 2,000,000 is not divisible by any of the primes in my list. If that is the case I am calling the number prime.
package main
import ("fmt"
"time"
)
func find_primes(max int) int {
// list of all primes that we find
var primes int
primes = append(primes, 2)
var is_prime = true
for i:=3; i<=max; i++ {
is_prime = false
// only odds can be prime
if i%2 != 0 {
is_prime = true
// should not be divisible by any previous
// prime numbers
for _, x := range primes {
if i%x == 0 {
is_prime = false
break
}
}
}
if is_prime {
primes = append(primes, i)
}
}
return primes
}
// just sume up all of the primes
func sum_primes(primes int) int {
var total int = 0
for _, x := range primes {
total = total + x
}
return total
}
func main() {
start := time.Now()
// find all primes less than 2,000,000
primes := find_primes(2000000)
sum := sum_primes(primes)
fmt.Println(sum)
t := time.Now()
elapsed := t.Sub(start)
fmt.Println(elapsed)
}
go
$endgroup$
I am trying to find all primes less than 2,000,000 and sum them together. My code currently takes 1'36" to run. Is there a faster way to get my solution?
The logic I am following in this code is make a list of all primes I have found. Then check that every odd number less than 2,000,000 is not divisible by any of the primes in my list. If that is the case I am calling the number prime.
package main
import ("fmt"
"time"
)
func find_primes(max int) int {
// list of all primes that we find
var primes int
primes = append(primes, 2)
var is_prime = true
for i:=3; i<=max; i++ {
is_prime = false
// only odds can be prime
if i%2 != 0 {
is_prime = true
// should not be divisible by any previous
// prime numbers
for _, x := range primes {
if i%x == 0 {
is_prime = false
break
}
}
}
if is_prime {
primes = append(primes, i)
}
}
return primes
}
// just sume up all of the primes
func sum_primes(primes int) int {
var total int = 0
for _, x := range primes {
total = total + x
}
return total
}
func main() {
start := time.Now()
// find all primes less than 2,000,000
primes := find_primes(2000000)
sum := sum_primes(primes)
fmt.Println(sum)
t := time.Now()
elapsed := t.Sub(start)
fmt.Println(elapsed)
}
go
go
asked 8 mins ago
The NightmanThe Nightman
1707
1707
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