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 C");
    for (int index = primeCount-12; 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
        print("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(newTotal: primes.count, startTime: startTime)
        }
    }

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

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

sample_output.text

$>$> git clone https://gist.github.com/d1f19a11d539e609fb16fc0d4d048d07.git

$> xcrun -sdk macosx swiftc -v
Apple Swift version 3.0-dev (LLVM dffa09ffd8, Clang 1e6cba3ce3, Swift d2aee43220)
Target: x86_64-apple-macosx10.9
 $> xcrun -sdk macosx swiftc -Ounchecked prime.swift
 $> ./prime
Total time: 0.168334007263184, calculated: 262144, per second: 1557284.854451
Total time: 0.439334034919739, calculated: 524288, per second: 1193369.86968419
Total time: 0.775188982486725, calculated: 786432, per second: 1014503.58269697
Total time: 1.1577240228653, calculated: 1048576, per second: 905721.898561662
Total time: 1.58434802293777, calculated: 1310720, per second: 827292.981733647
Total time: 2.04609698057175, calculated: 1572864, per second: 768714.296015671
Total time: 2.54207599163055, calculated: 1835008, per second: 721854.109020155
Total time: 2.87144201993942, calculated: 2000000, per second: 696514.150768816

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

 $> /usr/local/Cellar/gcc/5.3.0/bin/gcc-5 -v
 Using built-in specs.
 COLLECT_GCC=/usr/local/Cellar/gcc/5.3.0/bin/gcc-5
 COLLECT_LTO_WRAPPER=/usr/local/Cellar/gcc/5.3.0/libexec/gcc/x86_64-apple-darwin15.0.0/5.3.0/lto-wrapper
 Target: x86_64-apple-darwin15.0.0
 Configured with: ../configure --build=x86_64-apple-darwin15.0.0 --prefix=/usr/local/Cellar/gcc/5.3.0 --libdir=/usr/local/Cellar/gcc/5.3.0/lib/gcc/5 --enable-languages=c,c++,objc,obj-c++,fortran --program-suffix=-5 --with-gmp=/usr/local/opt/gmp --with-mpfr=/usr/local/opt/mpfr --with-mpc=/usr/local/opt/libmpc --with-isl=/usr/local/opt/isl --with-system-zlib --enable-libstdcxx-time=yes --enable-stage1-checking --enable-checking=release --enable-lto --with-build-config=bootstrap-debug --disable-werror --with-pkgversion='Homebrew gcc 5.3.0' --with-bugurl=https://github.com/Homebrew/homebrew/issues --enable-plugin --disable-nls --enable-multilib
 Thread model: posix
 gcc version 5.3.0 (Homebrew gcc 5.3.0)
  $> /usr/local/Cellar/gcc/5.3.0/bin/gcc-5 -Ofast -framework CoreFoundation -o prime_c prime.c
  $> ./prime_c
 Total time: 0.185617, calculated: 262144, per second: 1412284.209431
 Total time: 0.485510, calculated: 524288, per second: 1079870.537489
 Total time: 0.857549, calculated: 786432, per second: 917069.449400
 Total time: 1.287324, calculated: 1048576, per second: 814539.300731
 Total time: 1.767529, calculated: 1310720, per second: 741555.013814
 Total time: 2.292153, calculated: 1572864, per second: 686195.031235
 Total time: 2.848667, calculated: 1835008, per second: 644163.738173
 Total time: 3.219280, calculated: 2000000, per second: 621256.926146

 Primes calculated in C
 Prime[1999988] = 32452631
 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