static void Main(string[] args)
{
// Demonstrate("Naive division (Procedural)", DivisionPrimes.Create);
// Demonstrate("Caching division-based (Object-oriented)", PrimeList.Create);
// Demonstrate("Sieve of Eratosthenes (Object-oriented)", EratosthenesSieve.Create);
IPrimesGenerator primes =
Demonstrate("Caching Sieve of Eratosthenes (Object-oriented)", CachingEratosthenesSieve.Create);
// Demonstrate("Division-based (Functional)", PrimeNumbers.Create);
// Demonstrate("Caching division-based (Functional)", CachingPrimeNumbers.Create);
// Demonstrate("Parallel division-based (Functional)", ParallelPrimeNumbers.Create);
long sumOfFirst1M = primes.GetAll()
.Take(1_000_000)
.Sum(x => (long)x);
long sumBelow1M = primes.GetAll()
.TakeWhile(prime => prime <= 1_000_000)
.Sum(x => (long)x);
IEnumerable <int> periodic1Mth = primes.GetAll()
.Select((prime, index) => (prime: prime, index: index))
.Where(tuple => (tuple.index + 1) % 1_000_000 == 0)
.Select(tuple => tuple.prime)
.Take(5);
string periodic1MthReport = string.Join(" ",
periodic1Mth.Select((prime, index) => $"{index + 1}/{prime,-11:#,##0}"));
IEnumerable <int> groupCounts1M = primes.GetAll()
.TakeWhile(prime => prime <= 5_000_000)
.GroupBy(prime => prime / 1_000_000)
.Select(group => group.Count());
string groupCounts1MReport = string.Join(" ",
groupCounts1M.Select((count, index) => $"{index + 1}/{count,-11:#,##0}"));
IEnumerable <int> mersenePrimes = primes.GetAll()
.Where(prime => (prime + 1).IsPowerOf2())
.Take(7);
string mersenePrimesReport = string.Join(" ",
mersenePrimes.Select((prime, index) => $"{index + 1}/{prime:#,##0}"));
Console.WriteLine($" Sum of 1M primes: {sumOfFirst1M:#,##0}");
Console.WriteLine($" Sum below 1M: {sumBelow1M:#,##0}");
Console.WriteLine($" Millionth primes: {periodic1MthReport}");
Console.WriteLine($" Count per million: {groupCounts1MReport}");
Console.WriteLine($" Mersene primes: {mersenePrimesReport}");
}
static IPrimesGenerator Demonstrate(string label, Func <IPrimesGenerator> primesFactory)
{
Console.WriteLine(label);
IPrimesGenerator generator = primesFactory();
int start = 1_000_000;
int step = 1_000_000;
TimeSpan maxTime = TimeSpan.FromSeconds(10);
for (int pass = 0; pass < 2; pass += 1)
{
Stopwatch simulationClock = Stopwatch.StartNew();
Console.WriteLine();
int max = start - step;
while (simulationClock.Elapsed < maxTime)
{
max += step;
Stopwatch clock = Stopwatch.StartNew();
int count = generator.GetAll()
.TakeWhile(prime => prime <= max).Count();
Console.WriteLine(
$"{max,15:#,##0} " +
$"{count,10:#,##0} " +
$"{clock.Elapsed,12:mm\\:ss\\:fff}");
if (pass > 0 && max >= start + 2 * step)
{
break;
}
}
start = Math.Max(max - 2 * step, start);
}
Console.WriteLine(new string('-', 60));
return(generator);
}