这是 Partitioner.Create(int fromInclusive, int toExclusive) 中的错误吗？

Question

我想我在方法 Partitioner.Create(int fromInclusive, int toExclusive) 中发现了一个错误。当范围超过 Int32.MaxValue 时，它会为未提供的参数 rangeSize 计算负值。这是演示该问题的代码示例：

var partitioner = Partitioner.Create(-1, Int32.MaxValue);
var partitions = partitioner.GetPartitions(1);
foreach (var partition in partitions)
{
    while (partition.MoveNext())
    {
        var range = partition.Current;
        Console.WriteLine($"Range: {range.Item1,11} => {range.Item2,11}");
    }
}

输出：

Range:          -1 =>  -178956971
Range:  -178956971 =>  -357913941
Range:  -357913941 =>  -536870911
Range:  -536870911 =>  -715827881
Range:  -715827881 =>  -894784851
Range:  -894784851 => -1073741821
Range: -1073741821 => -1252698791
Range: -1252698791 => -1431655761
Range: -1431655761 => -1610612731
Range: -1610612731 => -1789569701
Range: -1789569701 => -1968526671
Range: -1968526671 => -2147483641
Range: -2147483641 =>  2147483647

因此，使用 for (int i = range.Item1; i < range.Item2; i++) 循环抛出这些范围将导致除最后一个范围外的所有范围都为零循环，这将有效循环 Int32 类型的整个范围。

有一个特例。下面的分区程序计算出 rangeSize 为 1.

Partitioner.Create(Int32.MinValue, Int32.MaxValue);

这里是方法的source code：

public static OrderablePartitioner<Tuple<int, int>> Create(
    int fromInclusive, int toExclusive)
{
    // How many chunks do we want to divide the range into?  If this is 1, then the
    // answer is "one chunk per core".  Generally, though, you'll achieve better
    // load balancing on a busy system if you make it higher than 1.
    int coreOversubscriptionRate = 3;

    if (toExclusive <= fromInclusive) throw new ArgumentOutOfRangeException("toExclusive");
    int rangeSize = (toExclusive - fromInclusive) /
        (PlatformHelper.ProcessorCount * coreOversubscriptionRate);
    if (rangeSize == 0) rangeSize = 1;
    return Partitioner.Create(CreateRanges(fromInclusive, toExclusive, rangeSize),
        EnumerablePartitionerOptions.NoBuffering); // chunk one range at a time
}

似乎在减法toExclusive - fromInclusive时发生了整数溢出。

如果这确实是一个错误，在 .NET Framework 的未来版本中修复它之前，您建议采用什么解决方法？

Answer 1

It seems that an integer overflow occurs on the division toExclusive - fromInclusive.

是的，看起来是一个错误。

What workaround do you suggest until it is fixed in a future version of the .NET Framework?

我建议将您的输入转换为 long 并改为调用 that version。 它仍然有类似的溢出错误，但如果您的原始输入是 int，您肯定不会运行进入 long 的溢出场景。

Answer 2

@mjwills 是对的。

这是一个错误，我已记录一个问题以在 .NET Core 的未来版本中修复此问题https://github.com/dotnet/corefx/issues/40201

并且建议的解决方法也是正确的。只需将输入参数转换为 long.

这是 Partitioner.Create(int fromInclusive, int toExclusive) 中的错误吗？

Is this a bug in Partitioner.Create(int fromInclusive, int toExclusive)?

.net

c#

partitioning

task-parallel-library