我正在寻找将数组拆分为固定大小的块的最快方法(当然,最后一个可以更小)。我浏览了整个网站,没有发现任何性能方面的比较,所以我写了它们,结果如下:
时间(以微秒为单位),平均值/误差/标准差
For int[]
- 30.02 | 0.1002 | 0.0937
For IEnumerable<int>
- 76.67 | 0.2146 | 0.2146 0.1902
Update:下面的版本(在 @Markus 的回答中)是 139.5 | 0.6702 | 0.5597
SO 上最受欢迎的方法,也是经常推荐的使用 LINQ 的方法GroupBy
with index/chunkSize
不行——267 微秒比上述任何一个实现都长太多了。
有没有更快的方法来分割数组?
附:
这是代码Array
and IEnumerable<T>
:
/// <summary>
/// Splits <paramref name="source"/> into chunks of size not greater than <paramref name="chunkMaxSize"/>
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="source">Array to be split</param>
/// <param name="chunkMaxSize">Max size of chunk</param>
/// <returns><see cref="IEnumerable{T}"/> of <see cref="Array"/> of <typeparam name="T"/></returns>
public static IEnumerable<T[]> AsChunks<T>(this T[] source, int chunkMaxSize)
{
var pos = 0;
var sourceLength = source.Length;
do
{
var len = Math.Min(pos + chunkMaxSize, sourceLength) - pos;
if (len == 0)
{
yield break;;
}
var arr = new T[len];
Array.Copy(source, pos, arr, 0, len);
pos += len;
yield return arr;
} while (pos < sourceLength);
}
/// <summary>
/// Splits <paramref name="source"/> into chunks of size not greater than <paramref name="chunkMaxSize"/>
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="source"><see cref="IEnumerable{T}"/> to be split</param>
/// <param name="chunkMaxSize">Max size of chunk</param>
/// <returns><see cref="IEnumerable{T}"/> of <see cref="Array"/> of <typeparam name="T"/></returns>
public static IEnumerable<T[]> AsChunks<T>(this IEnumerable<T> source, int chunkMaxSize)
{
var arr = new T[chunkMaxSize];
var pos = 0;
foreach (var item in source)
{
arr[pos++] = item;
if (pos == chunkMaxSize)
{
yield return arr;
arr = new T[chunkMaxSize];
pos = 0;
}
}
if (pos > 0)
{
Array.Resize(ref arr, pos);
yield return arr;
}
}
P.P.S 带有 BenchmarkDotNet 测试的完整解决方案是在 GitHub 上 https://github.com/AlexSeleznyov/SplitToChunk.