Swift vs C Prime Number Benchmark

prime.c

// code originally adapted from https://github.com/DuncanMC/SwiftPerformanceBenchmark

#include <stdlib.h>
#include <stdio.h>
#include <CoreFoundation/CFDate.h>

void updateTotal(int newTotal, CFAbsoluteTime startTime) {
    
    CFAbsoluteTime now = CFAbsoluteTimeGetCurrent();
    CFAbsoluteTime totalTime = now - startTime;
    printf("Total time: %f, calculated: %d, per second: %f\n", totalTime, newTotal, newTotal / totalTime);
    
    
}


int main(int argc, const char * argv[]) {

    int totalCount = 2000000;
    int primeCount = 1;
    int *primes = (int *)malloc(sizeof(int) * totalCount);
    primes[0] = 2;
    CFAbsoluteTime startTime = CFAbsoluteTimeGetCurrent();
    
    int candidate = 3;
    int isPrime = 0;
    
    while (primeCount < totalCount)
    {
        isPrime = 1;
        //Loop through all the primes we've already found.
        for (int i = 0; i < primeCount; ++i)
        {
            int oldPrime = primes[i];
            if (candidate % oldPrime == 0)
            {
                isPrime = 0;
                break;
            }
            if (candidate < oldPrime * oldPrime)
            {
                isPrime = 1;
                break;
            }
        }

        if (isPrime)
        {
            primes[primeCount++] = candidate;
            if ((primeCount & 0x3ffff) == 0)
            {
                updateTotal(primeCount, startTime);
            }
        }
        //Move on to the next (odd) number.
        candidate += 2;
        
    }
    updateTotal(primeCount, startTime);
    
    printf("\nPrimes calculated in Swift");
    for (int index = primeCount-11; index < primeCount; index++)
    {
        int aPrime = primes[index];
        printf("Prime[%d] = %d\n",index,aPrime);
    }
    
    return 0;
}

prime.swift

// code originally adapted from https://github.com/DuncanMC/SwiftPerformanceBenchmark

import CoreFoundation.CFDate

func updateTotal(newTotal: Int, startTime: CFAbsoluteTime) {

        let now = CFAbsoluteTimeGetCurrent()
        let totalTime = now - startTime
        println("Total time: \(totalTime), calculated: \(newTotal), per second: \(Double(newTotal)/totalTime)")

}


let totalCount = 2_000_000
var primes: [CInt] = []
primes.reserveCapacity(totalCount)
primes.append(2)
let startTime = CFAbsoluteTimeGetCurrent()

var candidate: CInt = 3
var isPrime: Bool = false

while primes.count < totalCount
{
    isPrime = true
    //Loop through all the primes we've already found.
    for oldPrime in primes
    {
        if candidate % oldPrime == 0
        {
            isPrime = false
            break
        }
        if candidate < oldPrime &* oldPrime
        {
            isPrime = true
            break
        }
    }
    if isPrime
    {
        primes.append(candidate)
        if (primes.count & 0x3ffff) == 0
        {
            updateTotal(primes.count, startTime)
        }
    }

    //Move on to the next (odd) number.
    candidate += 2
    
}
updateTotal(primes.count, startTime)

//println("Checking for swift completion block")

//print the last 10 primes calculated
println("\nPrimes calculated in Swift")
for idx in (primes.endIndex-11)..<primes.endIndex
{
    println("Prime[\(idx)] = \(primes[idx])")
}

sample_output.text

 ~/src [1] % swiftc --version
Apple Swift version 1.2 (swiftlang-602.0.47.4 clang-602.0.48)
Target: x86_64-apple-darwin14.3.0
 ~/src [2] % swiftc -O -o prime_swift prime.swift
 ~/src [3] % ./prime_swift
Total time: 0.499701023101807, calculated: 262144, per second: 524601.687570674
Total time: 1.30302101373672, calculated: 524288, per second: 402363.426585484
Total time: 2.25548201799393, calculated: 786432, per second: 348675.801325816
Total time: 3.38296902179718, calculated: 1048576, per second: 309957.31655945
Total time: 4.62443399429321, calculated: 1310720, per second: 283433.605413656
Total time: 5.96368700265884, calculated: 1572864, per second: 263740.199527366
Total time: 7.38956499099731, calculated: 1835008, per second: 248324.225070838
Total time: 8.30392301082611, calculated: 2000000, per second: 240850.017201813

Primes calculated in Swift
Prime[1999989] = 32452649
Prime[1999990] = 32452657
Prime[1999991] = 32452681
Prime[1999992] = 32452687
Prime[1999993] = 32452727
Prime[1999994] = 32452759
Prime[1999995] = 32452781
Prime[1999996] = 32452789
Prime[1999997] = 32452837
Prime[1999998] = 32452841
Prime[1999999] = 32452843
 ~/src [4] % cc --version
Apple LLVM version 6.1.0 (clang-602.0.48) (based on LLVM 3.6.0svn)
Target: x86_64-apple-darwin14.3.0
Thread model: posix
 ~/src [5] % cc -Ofast -framework CoreFoundation -o prime_c prime.c
 ~/src [6] % ./prime_c
Total time: 0.443690, calculated: 262144, per second: 590826.926095
Total time: 1.189520, calculated: 524288, per second: 440755.934644
Total time: 2.095344, calculated: 786432, per second: 375323.573297
Total time: 3.170024, calculated: 1048576, per second: 330778.564339
Total time: 4.350820, calculated: 1310720, per second: 301258.153293
Total time: 5.646417, calculated: 1572864, per second: 278559.658973
Total time: 7.035104, calculated: 1835008, per second: 260835.943651
Total time: 7.955803, calculated: 2000000, per second: 251388.827850

Primes calculated in SwiftPrime[1999989] = 32452649
Prime[1999990] = 32452657
Prime[1999991] = 32452681
Prime[1999992] = 32452687
Prime[1999993] = 32452727
Prime[1999994] = 32452759
Prime[1999995] = 32452781
Prime[1999996] = 32452789
Prime[1999997] = 32452837
Prime[1999998] = 32452841
Prime[1999999] = 32452843
 ~/src [7] %