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// Code adapted from:
// http://alaska-kamtchatka.blogspot.com/2009/05/is-immutable-data-slow.html

// Java code
public final class MutTest {
    private static final class Person0 {
        public final String name;
        public final int age;
        public final double balance;

public Person0(String name, int age, double balance) {
            this.name = name;
            this.age = age;
            this.balance = balance;
        }

public Person0 deposit(double amount) {
            return new Person0(this.name, this.age, this.balance + amount);
        }
    }

private static final class Person1 {
        public String name;
        public int age;
        public double balance;

public Person1(String name, int age, double balance) {
            this.name = name;
            this.age = age;
            this.balance = balance;
        }

public void deposit(double amount) {
            this.balance += amount;
        }
    }

private interface Test {
        double test(int iters);
    }

private static final Test TEST0 = new Test() {
        public double test(int iters) {
            Person0 person = new Person0("John Doe", 19, 100.0);
            for (int i = 0; i != iters; i++) {
                person = person.deposit(1.0);
            }
            return person.balance;
        }
    };

private static final Test TEST1 = new Test() {
        public double test(int iters) {
            Person1 person = new Person1("John Doe", 19, 100.0);
            for (int i = 0; i != iters; i++) {
                person.deposit(1.0);
            }
            return person.balance;
        }
    };

private static int test(int times, Test test, int iters) {
        long best = Long.MAX_VALUE;
        double balance;
        for (int i = 0; i != times; i++) {
            long now = System.currentTimeMillis();
            balance = test.test(iters);
            now = System.currentTimeMillis() - now;
            if (best > now)
                best = now;
        }
        return (int)((double) iters / ((double) best / 1000.0));
    }

public static void main(String[] args) {
        final int iters = 100000000;
        System.out.printf("Immutable record: %d updates/s\n", test(5, TEST0, iters));
        System.out.printf("Mutable record:   %d updates/s\n", test(5, TEST1, iters*4));
    }
}

/*
Java server:
Immutable record:  48_520_135 updates/s
Mutable record:   634_920_634 updates/s (13.1 X)
*/

-------------------------------------

// D1 code
import tango.stdc.stdio: printf;
import tango.time.StopWatch: StopWatch;

StopWatch elapsed;

final class Person0 {
    final char[] name;
    final double balance;
    final int age;

this(char[] name, int age, double balance) {
        this.name = name;
        this.age = age;
        this.balance = balance;
    }

final Person0 deposit(double amount) {
        return new Person0(this.name, this.age, this.balance + amount);
    }
}

final class Person1 {
    char[] name;
    double balance;
    int age;

this(char[] name, int age, double balance) {
        this.name = name;
        this.age = age;
        this.balance = balance;
    }

final void deposit(double amount) {
        this.balance += amount;
    }
}

public double test0(int iters) {
    auto person = new Person0("John Doe", 19, 100.0);
    for (int i = 0; i != iters; i++)
        person = person.deposit(1.0);
    return person.balance;
}

public double test1(int iters) {
    auto person = new Person1("John Doe", 19, 100.0);
    for (int i = 0; i != iters; i++)
        person.deposit(1.0);
    return person.balance;
}

int test(TyFun)(int times, TyFun test, int iters) {
    double best = double.max;
    double balance;
    for (int i = 0; i != times; i++) {
        elapsed.start;
        balance = test(iters);
        double now = elapsed.stop;
        if (best > now)
            best = now;
    }
    return cast(int)(iters / best);
}

void main() {
    const int iters = 10_000_000;
    printf("Immutable record: %d updates/s\n", test(5, &test0, iters));
    printf("Mutable record:   %d updates/s\n", test(5, &test1, iters*60)); // requires an higher iters!
}

/*
Immutable record:   3_773_527 updates/s
Mutable record:   631_569_640 updates/s (167 X)
*/

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