C# 在数组上很慢？ [关闭]

Question

我正在处理 CT 图像，因此需要大量操作 3D 数组，但发现 C# 处理数组非常慢。我写了一个简单的 BFS 测试，基于https://stackoverflow.com/a/1056091:

struct Vector
{
    public int X, Y, Z;
}
int width = 512, height = 512, depth = 200;
public static int bfs(int[, ,] matrix)
{
    bool[, ,] visited = new bool[width, height, depth];
    int sum = 0;
    Queue<Vector> queue = new Queue<Vector>();
    queue.Enqueue(new Vector { X = 0, Y = 0, Z = 0 });
    while (queue.Count > 0)
    {
        Vector c = queue.Dequeue();
        int cx = c.X;
        int cy = c.Y;
        int cz = c.Z;
        sum += matrix[cx, cy, cz];
        int x, y, z;

        if ((x = cx - 1) >= 0 && !visited[x, cy, cz])
        { queue.Enqueue(new Vector { X = x, Y = cy, Z = cz }); visited[x, cy, cz] = true; }
        if ((y = cy - 1) >= 0 && !visited[cx, y, cz])
        { queue.Enqueue(new Vector { X = cx, Y = y, Z = cz }); visited[cx, y, cz] = true; }
        if ((z = cz - 1) >= 0 && !visited[cx, cy, z])
        { queue.Enqueue(new Vector { X = cx, Y = cy, Z = z }); visited[cx, cy, z] = true; }
        if ((x = cx + 1) < width && !visited[x, cy, cz])
        { queue.Enqueue(new Vector { X = x, Y = cy, Z = cz }); visited[x, cy, cz] = true; }
        if ((y = cy + 1) < height && !visited[cx, y, cz])
        { queue.Enqueue(new Vector { X = cx, Y = y, Z = cz }); visited[cx, y, cz] = true; }
        if ((z = cz + 1) < depth && !visited[cx, cy, z])
        { queue.Enqueue(new Vector { X = cx, Y = cy, Z = z }); visited[cx, cy, z] = true; }
    }
    return sum;
}
public static void TestTime<T, TR>(Func<T, TR> action, T obj, int iterations)
{
    Stopwatch stopwatch = Stopwatch.StartNew();
    for (int i = 0; i < iterations; ++i)
        action(obj);
    Console.WriteLine(action.Method.Name + " took " + stopwatch.Elapsed);
}
static void Main(string[] args)
{
    Random random = new Random();
    int[, ,] m1 = new int[width, height, depth];
    for (int x = 0; x < width; ++x)
        for (int y = 0; y < height; ++y)
            for (int z = 0; z < depth; ++z)
                m1[x, y, z] = random.Next();
    const int iterations = 1;
    TestTime<int[, ,], int>(bfs, m1, iterations);
    TestTime<int[, ,], int>(bfs, m1, iterations);
}

这需要大约 23 秒（一次迭代）。用VS2012编译，“Release”d，优化。尝试编写类似的 C++ 代码（使用堆栈分配的数组），大约需要 0.08 秒。 DFS（使用堆栈而不是队列）运行速度较慢。一维或锯齿状阵列给出几乎相同的结果。 我应该注意到连续访问（如Why are multi-dimensional arrays in .NET slower than normal arrays?）运行良好，[512x512x200] 数组的 100 次迭代在 ~26 秒内。

为什么在 C# 中非连续数组访问如此缓慢？有什么办法可以加快速度吗？

Answer 1

我改用 list+struct 看看是否有帮助。它把时间减半。我将多维数组更改为使用单维并手动将索引器相乘。如果有的话，那就更糟了。

struct Q
{
    public int X, Y, Z;
}
public static int bfs(int[, ,] matrix)
{
    int d1 = matrix.GetLength(0), d2 = matrix.GetLength(1), d3 = matrix.GetLength(2);
    var visited = new bool[d1, d2, d3];
    int sum = 0;
    var q = new List<Q>();
    q.Add(new Q());
    while (q.Count > 0)
    {
        var last = q[q.Count - 1];
        q.RemoveAt(q.Count - 1);
        int cx = last.X;
        int cy = last.Y;
        int cz = last.Z;
        sum += matrix[cx, cy, cz];
        int x, y, z;

        if ((x = cx - 1) >= 0 && !visited[x, cy, cz])
        { q.Add(new Q{X = x, Y = cy, Z = cz}); visited[x, cy, cz] = true; 
...