/// <summary>
/// Executes a serial for loop.
/// </summary>
/// <param name="i0">The start index (inclusive).</param>
/// <param name="i1">The end index (exclusive).</param>
/// <param name="action">The action that is invoked once per iteration.</param>
private static void SerialFor(int i0, int i1, Alt.Action <int> action)
{
for (int i = i0; i < i1; i++)
{
action(i);
}
}
/// <summary>
/// Executes a parallel for loop using ThreadPool.
/// </summary>
/// <param name="i0">The start index (inclusive).</param>
/// <param name="i1">The end index (exclusive).</param>
/// <param name="action">The action that is invoked once per iteration.</param>
private static void ParallelFor(int i0, int i1, Alt.Action <int> action)
{
// Environment.ProcessorCount is not available here. Use 4 processors.
int p = 4;
// Initialize wait handles
var doneEvents = new System.Threading.WaitHandle[p];
for (int i = 0; i < p; i++)
{
doneEvents[i] = new System.Threading.ManualResetEvent(false);
}
// Invoke the action of a partition of the range
Alt.Action <int, int, int> invokePartition = (k, j0, j1) =>
{
for (int i = j0; i < j1; i++)
{
action(i);
}
((System.Threading.ManualResetEvent)doneEvents[k]).Set();
};
// Start p background threads
int n = (i1 - i0 + p - 1) / p;
for (int i = 0; i < p; i++)
{
int k = i;
int j0 = i0 + (i * n);
var j1 = Math.Min(j0 + n, i1);
System.Threading.ThreadPool.QueueUserWorkItem(state => invokePartition(k, j0, j1));
}
// Wait for the threads to finish
foreach (var wh in doneEvents)
{
wh.WaitOne();
}
}
