/// <summary>
/// 2.
/// Create a static method called CalcPrimes
/// that accepts a first and last number and a maximum degree of parallelism (an integer)
/// and returns a list of prime numbers in that range.
/// Use the Parallel class.
/// Make sure you add items to the collection in a thread-safe way.
/// Use a lambda expression to execute the body of the parallel loop
/// </summary>
/// <param name="first"></param>
/// <param name="last"></param>
/// <param name="maxParallelDegree"></param>
/// <returns></returns>
static List <int> Lab1CalcPrimes(int first, int last, int maxParallelDegree)
{
var primesInRange = new List <int>();
var primesRange = new List <int> [maxParallelDegree];
for (int i = 0; i < maxParallelDegree; i++)
{
primesRange[i] = new List <int>();
}
int range = (int)Math.Floor((double)(((last - first) / maxParallelDegree)));
var primeCalc = new PrimesCalculator();
var option = new ParallelOptions();
option.MaxDegreeOfParallelism = maxParallelDegree;
Parallel.For(0, maxParallelDegree - 1, option, (i) =>
{
primeCalc.CalcPrimes((int)(first + i * range), (int)(first + (i + 1) * range), primesRange[i]);
}
);
for (int i = 0; i < maxParallelDegree; i++)
{
if (primesRange[i] != null)
{
primesInRange.AddRange(primesRange[i]);
}
}
return(primesInRange);
}
/// <summary>
/// 3.
/// Call CalcPrimes from the Main method and compare its performance with a sequential implementation,
/// by creating a ParallelOptions instance and setting its MaxDegreeOfParallelism property to the passed number.
/// </summary>
/// <param name="args"></param>
///1. Continue from the previous exercise.
static void Main(string[] args)
{
#region lab1
int first = 0, last = 700, maxParallelDegree = 4;
var outputList = new List <int>();
var sincCalc = new PrimesCalculator();
var watch = new Stopwatch();
for (int i = 1; i < 17; i++)
{
watch.Restart();
Lab1CalcPrimes(first, last, maxParallelDegree);
watch.Stop();
Console.WriteLine($"the parllel calc took {watch.ElapsedTicks} Ticks, with {i} maxParlleldeg");
}
watch.Restart();
sincCalc.CalcPrimes(first, last, outputList);
watch.Stop();
Console.WriteLine($"the sinc calc took {watch.ElapsedTicks} Ticks");
#endregion
#region lab2
last = 30000000;
outputList = CalcPrimes(first, last);
Console.WriteLine($"{outputList.Count} is how many numbers returned before being cancelled");
#endregion
}
///1. Continue from the previous exercise.
///2. Change the signature of CalcPrimes to accept two integers and nothing else. Remove the ParallelOptions object and use the default degree of parallelism.
///3. We want to cancel the operation randomly.Add a Random instance in the CalcPrimes method before the parallel loop starts.
///4. The lambda expression should accept a ParallelLoopState variable as well as the loop index.Look at the other overloads of Parallel.For.
///5. In the lambda expression, call Random.Next with 10000000 as argument, and check for the return of zero. If it is, call the Stop method of ParallelLoopState.
///6. Call CalcPrimes from Main with the last number as 30000000 and display how many numbers returned before being cancelled.
static List <int> CalcPrimes(int first, int last)
{
int maxParallelDegree = 7;
var primesInRange = new List <int>();
var primesRange = new List <int> [maxParallelDegree];
for (int i = 0; i < maxParallelDegree; i++)
{
primesRange[i] = new List <int>();
}
int range = (int)Math.Floor((double)(((last - first) / maxParallelDegree)));
var primeCalc = new PrimesCalculator();
var rand = new Random();
Parallel.For(0, maxParallelDegree - 1, (i, state) =>
{
if (rand.Next(10000000) == 0)
{
state.Stop();
}
else
{
primeCalc.CalcPrimes((int)(first + i * range), (int)(first + (i + 1) * range), primesRange[i]);
}
}
);
for (int i = 0; i < maxParallelDegree; i++)
{
if (primesRange[i] != null)
{
primesInRange.AddRange(primesRange[i]);
}
}
return(primesInRange);
}