This document discusses optimizations made to code for finding prime numbers in Java and C++. It analyzes performance of different implementations, including using primitives vs wrappers, creating a PrimeFinder class, bringing the square root calculation inside the loop, and adding an is_prime method. Graphs show performance improvements from these changes, with the fastest implementations taking around 2-3 million nanoseconds to find primes up to 10,000.

1. Object Comparisons
Finding Prime Numbers
C++ & Java
ADAM FELDSCHER
I699 PERFORMANCE DESIGN PATTERNS II
10/16/2019

2. Modifications
 All tests are done for primes up to 10k, with 40 iterations
 1k had too much noise
 Java and C++
 Java Primitives vs Wrappers
 PrimeFinder Class Invoction
 New instance per each iteration
 Bring SQRT into for loop comparison
 Adding is_prime method

3. Algorithm (Java)
for (int iter = 0; iter < max_iter; iter++) {
// insert delays
long start_time = System.nanoTime();
for (int n = 2; n <= max_prime; n++) {// 2 - 10k
int max_divisor = (int) sqrt(n);
boolean is_prime = true;
for (int i = 2; i <= max_divisor; i++) {// check for divisors
if (n % i == 0) {
is_prime = false;
break;
}
}
if (is_prime) {
num_primes_found++; // count primes
}
}
long end_time = System.nanoTime();
// print things
num_primes_found = 0;
}

4. Java Consistency Check
0
1000000
2000000
3000000
4000000
5000000
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Nanoseconds
Iteration
Java 10, 10k, normal consistency
Run 1 Run 2

5. Java Primitives vs Wrappers

6. Java Primitives vs Wrappers
(Integer)
0
5000000
10000000
15000000
20000000
25000000
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Nanoseconds
Iteration
Java 10, 10k, Integer
Primative Integer

7. Java PrimeFinder Class
public class PrimeFinder {
private Integer max_prime;
public PrimeFinder(Integer max_prime) {
this.max_prime = max_prime;
}
public Integer find_primes() {
Integer num_primes_found = 0;
for (Integer n = 2; n <= max_prime; n++) {
Integer max_divisor = (int) sqrt(n);
Boolean is_prime = true;
for (Integer i = 2; i <= max_divisor; i++) {
if (n % i == 0) {
is_prime = false;
break;
}
}
if (is_prime) {
num_primes_found++;
}
}
return num_primes_found;
}
}
public static void main(String[] args) {
for (Integer iter = 0; iter < max_iter; iter++) {
//Start Timer
PrimeFinder primeFinder = new PrimeFinder(iter, max_prime);
num_primes_found = primeFinder.find_primes();
//End timer & Print
}

8. Java PrimeFinder Class
0
5000000
10000000
15000000
20000000
25000000
30000000
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Nanoseconds
Iteration
Java 10, 10k, Primefinder
Primative Class PrimeFinder

9. C++ PrimeFinder Class
class PrimeFinder
{
private:
int _max_prime;
public:
PrimeFinder(int max_prime);
int find_primes();
};
PrimeFinder::PrimeFinder(int max_prime) {
_max_prime = max_prime;
}
int PrimeFinder::find_primes() {
int num_primes_found = 0;
int n;
for (n = 2; n <= _max_prime; n++) {
int max_divisor = (int) sqrt(n);
bool is_prime = true;
int i;
for (i = 2; i <= max_divisor; i++) {
if (n % i == 0) {
is_prime = false;
break;
}
}
if (is_prime) {
num_primes_found++;
}
}
return num_primes_found;
}

10. C++ PrimeFinder Class
0
200000
400000
600000
800000
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Nanoseconds
Iteration
C++ PrimeFinder
C++ Primative C++ PrimeFinder

11. Java Prime Finder + SQRT

12. Java Prime Finder + SQRT
0
5000000
10000000
15000000
20000000
25000000
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Nanoseconds
Iteration
Java 10, 10k, Primefinder
Primative Class PrimeFinder SQRT

13. C++ PrimeFinder + SQRT
0
200000
400000
600000
800000
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Nanoseconds
Iteration
C++ PrimeFinder SQRT
C++ PrimeFinder C++ PrimeFinder SQRT

14. Java IsPrime Method
public class PrimeFinder {
private Boolean is_prime(Integer n) {
Integer max_divisor = (int) sqrt(n);
for (Integer i = 2; i <= max_divisor; i++) {
if (n % i == 0) {
return false;
}
}
return true;
}
public Integer find_primes() {
Integer num_primes_found = 0;
for (Integer n = 2; n <= max_prime; n++) {
if (is_prime(n)) {
num_primes_found++;
}
}
return num_primes_found;
}
}

15. Java IsPrime Method
0
5000000
10000000
15000000
20000000
25000000
30000000
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Nanoseconds
Iteration
Java 10, 10k, Integer, PrimeFinder, IsPrime
Primative Class PrimeFinder PrimeFinder IsPrime

16. C++ IsPrime Method
bool PrimeFinder::is_prime(int n) {
int max_divisor = (int) sqrt(n);
for (int i = 2; i <= max_divisor; i++) {
if (n % i == 0) {
return false;
}
}
return true;
}
int PrimeFinder::find_primes() {
int num_primes_found = 0;
int n;
for (n = 2; n <= _max_prime; n++) {
if (is_prime(n)) {
num_primes_found++;
}
}
return num_primes_found;
}

17. C++ IsPrime Method
0
200000
400000
600000
800000
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Nanoseconds
Iteration
C++ PrimeFinder isPrime
C++ PrimeFinder C++ PrimeFinder isprime

18. Java 1K tests
0
1000000
2000000
3000000
4000000
5000000
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Nanoseconds
Iteration
Java 10, 1k, Integer Primefinder
Integer Class PrimeFinder