//--------------------------------------------------------------------------
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// File: ParallelAlgorithms_For.cs
//
//--------------------------------------------------------------------------
using System.Collections.Generic;
using System.Numerics;
using System.Threading.Tasks;
namespace System.Threading.Algorithms
{
public static partial class ParallelAlgorithms
{
/// Executes a for loop in which iterations may run in parallel.
/// The start index, inclusive.
/// The end index, exclusive.
/// The delegate that is invoked once per iteration.
public static void For(BigInteger fromInclusive, BigInteger toExclusive, Action body)
{
For(fromInclusive, toExclusive, s_defaultParallelOptions, body);
}
/// Executes a for loop in which iterations may run in parallel.
/// The start index, inclusive.
/// The end index, exclusive.
/// A System.Threading.Tasks.ParallelOptions instance that configures the behavior of this operation.
/// The delegate that is invoked once per iteration.
public static void For(BigInteger fromInclusive, BigInteger toExclusive, ParallelOptions options, Action body)
{
// Determine how many iterations to run...
var range = toExclusive - fromInclusive;
// ... and run them.
if (range <= 0)
{
// If there's nothing to do, bail
return;
}
// Fast path
else if (range <= Int64.MaxValue)
{
// If the range is within the realm of Int64, we'll delegate to Parallel.For's Int64 overloads.
// Iterate from 0 to range, and then call the user-provided body with the scaled-back value.
Parallel.For(0, (long)range, options, i => body(i + fromInclusive));
}
// Slower path
else
{
// For a range larger than Int64.MaxValue, we'll rely on an enumerable of BigInteger.
// We create a C# iterator that yields all of the BigInteger values in the requested range
// and then ForEach over that range.
Parallel.ForEach(Range(fromInclusive, toExclusive), options, body);
}
}
/// Creates an enumerable that iterates the range [fromInclusive, toExclusive).
/// The lower bound, inclusive.
/// The upper bound, exclusive.
/// The enumerable of the range.
private static IEnumerable Range(BigInteger fromInclusive, BigInteger toExclusive)
{
for (var i = fromInclusive; i < toExclusive; i++) yield return i;
}
}
}