如何在C#中快速从一个ushort数组中减去另一个ushort数组？

我需要从ushort arrayB中具有相同长度的对应索引值中快速减去ushort arrayA中的每个值

另外，如果差值为负，我需要存储一个零，而不是负差值

（确切地说，长度=327680，因为我正在从另一个相同大小的图像中减去一个640x512图像）

下面的代码目前需要~20ms，如果可能的话，我希望将其降低到~5ms以下。不安全代码是可以的，但请提供一个例子，因为我不太擅长编写不安全代码

谢谢大家!

public ushort[] Buffer { get; set; }

public void SubtractBackgroundFromBuffer(ushort[] backgroundBuffer)
{
    System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
    sw.Start();

    int bufferLength = Buffer.Length;

    for (int index = 0; index < bufferLength; index++)
    {
        int difference = Buffer[index] - backgroundBuffer[index];

        if (difference >= 0)
            Buffer[index] = (ushort)difference;
        else
            Buffer[index] = 0;
    }

    Debug.WriteLine("SubtractBackgroundFromBuffer(ms): " + sw.Elapsed.TotalMilliseconds.ToString("N2"));
}

您可以尝试：

更新：我已经尝试过了，我发现在你的情况下有一个最小的差异，但是当数组变大时，差异也会变大

---

在实际执行减法之前，您可以先检查结果是否为负数，从而获得较小的性能提升。这样，如果结果为负数，则无需执行减法运算。例如：

if (Buffer[index] > backgroundBuffer[index])
    Buffer[index] = (ushort)(Buffer[index] - backgroundBuffer[index]);
else
    Buffer[index] = 0;

一些基准

SubtractBackgroundFromBuffer:

这是问题的原始方法

subtractbackgroundfromtbufferwithcalcopt:

这是一种原始的方法，它补充了TTat提高计算速度的思想

SubtractBackgroundFromBufferParallelFor:

从Selman22的答案中找出解决方案

SubtractBackgroundFromBufferBlockParallelFor:

我的答案。与3类似，但将处理分解为4096个值的块

SubtractBackgroundFromBufferPartitionedParallelForEach:

Geoff的第一个答案

SubtractBackgroundFromBufferPartitionedParallelForEachHack:

Geoff的第二个答案

更新

public static void SubtractBackgroundFromBuffer(ushort[] backgroundBuffer)
{
    int bufferLength = Buffer.Length;

    for (int index = 0; index < bufferLength; index++)
    {
        int difference = Buffer[index] - backgroundBuffer[index];

        if (difference >= 0)
            Buffer[index] = (ushort)difference;
        else
            Buffer[index] = 0;
    }
}

public static void SubtractBackgroundFromBufferWithCalcOpt(ushort[] backgroundBuffer)
{
    int bufferLength = Buffer.Length;

    for (int index = 0; index < bufferLength; index++)
    {
        if (Buffer[index] < backgroundBuffer[index])
        {
            Buffer[index] = 0;
        }
        else
        {
            Buffer[index] -= backgroundBuffer[index];
        }
    }
}

public static void SubtractBackgroundFromBufferParallelFor(ushort[] backgroundBuffer)
{
    Parallel.For(0, Buffer.Length, (i) =>
    {
        int difference = Buffer[i] - backgroundBuffer[i];
        if (difference >= 0)
            Buffer[i] = (ushort)difference;
        else
            Buffer[i] = 0;
    });
}        

public static void SubtractBackgroundFromBufferBlockParallelFor(ushort[] backgroundBuffer)
{
    int blockSize = 4096;

    Parallel.For(0, (int)Math.Ceiling(Buffer.Length / (double)blockSize), (j) =>
    {
        for (int i = j * blockSize; i < (j + 1) * blockSize; i++)
        {
            int difference = Buffer[i] - backgroundBuffer[i];

            Buffer[i] = (ushort)Math.Max(difference, 0);                    
        }
    });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEach(ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
        {
            for (int i = range.Item1; i < range.Item2; ++i)
            {
                if (Buffer[i] < backgroundBuffer[i])
                {
                    Buffer[i] = 0;
                }
                else
                {
                    Buffer[i] -= backgroundBuffer[i];
                }
            }
        });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEachHack(ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
    {
        for (int i = range.Item1; i < range.Item2; ++i)
        {
            unsafe
            {
                var nonNegative = Buffer[i] > backgroundBuffer[i];
                Buffer[i] = (ushort)((Buffer[i] - backgroundBuffer[i]) *
                    *((int*)(&nonNegative)));
            }
        }
    });
}

有趣的是，我可以通过使用（如Bruno Costa所建议的）从BufferBlockParallelfor中减去BackgroundFromBufferBlockParallelfor来获得一个小的速度提升（~6%）

而不是

if (difference >= 0)
    Buffer[i] = (ushort)difference;
else
    Buffer[i] = 0;

结果

public static void SubtractBackgroundFromBuffer(ushort[] backgroundBuffer)
{
    int bufferLength = Buffer.Length;

    for (int index = 0; index < bufferLength; index++)
    {
        int difference = Buffer[index] - backgroundBuffer[index];

        if (difference >= 0)
            Buffer[index] = (ushort)difference;
        else
            Buffer[index] = 0;
    }
}

public static void SubtractBackgroundFromBufferWithCalcOpt(ushort[] backgroundBuffer)
{
    int bufferLength = Buffer.Length;

    for (int index = 0; index < bufferLength; index++)
    {
        if (Buffer[index] < backgroundBuffer[index])
        {
            Buffer[index] = 0;
        }
        else
        {
            Buffer[index] -= backgroundBuffer[index];
        }
    }
}

public static void SubtractBackgroundFromBufferParallelFor(ushort[] backgroundBuffer)
{
    Parallel.For(0, Buffer.Length, (i) =>
    {
        int difference = Buffer[i] - backgroundBuffer[i];
        if (difference >= 0)
            Buffer[i] = (ushort)difference;
        else
            Buffer[i] = 0;
    });
}        

public static void SubtractBackgroundFromBufferBlockParallelFor(ushort[] backgroundBuffer)
{
    int blockSize = 4096;

    Parallel.For(0, (int)Math.Ceiling(Buffer.Length / (double)blockSize), (j) =>
    {
        for (int i = j * blockSize; i < (j + 1) * blockSize; i++)
        {
            int difference = Buffer[i] - backgroundBuffer[i];

            Buffer[i] = (ushort)Math.Max(difference, 0);                    
        }
    });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEach(ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
        {
            for (int i = range.Item1; i < range.Item2; ++i)
            {
                if (Buffer[i] < backgroundBuffer[i])
                {
                    Buffer[i] = 0;
                }
                else
                {
                    Buffer[i] -= backgroundBuffer[i];
                }
            }
        });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEachHack(ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
    {
        for (int i = range.Item1; i < range.Item2; ++i)
        {
            unsafe
            {
                var nonNegative = Buffer[i] > backgroundBuffer[i];
                Buffer[i] = (ushort)((Buffer[i] - backgroundBuffer[i]) *
                    *((int*)(&nonNegative)));
            }
        }
    });
}

请注意，这是每次运行中1000次迭代的总时间

SubtractBackgroundFromBuffer(ms):                                 2,062.23 
SubtractBackgroundFromBufferWithCalcOpt(ms):                      2,245.42
SubtractBackgroundFromBufferParallelFor(ms):                      4,021.58
SubtractBackgroundFromBufferBlockParallelFor(ms):                   769.74
SubtractBackgroundFromBufferPartitionedParallelForEach(ms):         827.48
SubtractBackgroundFromBufferPartitionedParallelForEachHack(ms):     539.60

因此，从这些结果来看，最好的方法是将计算优化结合起来，以获得较小的增益，并利用

Parallel.for

对图像块进行操作。当然，您的里程数会有所不同，并行代码的性能对您运行的CPU非常敏感

测试线束

public static void SubtractBackgroundFromBuffer(ushort[] backgroundBuffer)
{
    int bufferLength = Buffer.Length;

    for (int index = 0; index < bufferLength; index++)
    {
        int difference = Buffer[index] - backgroundBuffer[index];

        if (difference >= 0)
            Buffer[index] = (ushort)difference;
        else
            Buffer[index] = 0;
    }
}

public static void SubtractBackgroundFromBufferWithCalcOpt(ushort[] backgroundBuffer)
{
    int bufferLength = Buffer.Length;

    for (int index = 0; index < bufferLength; index++)
    {
        if (Buffer[index] < backgroundBuffer[index])
        {
            Buffer[index] = 0;
        }
        else
        {
            Buffer[index] -= backgroundBuffer[index];
        }
    }
}

public static void SubtractBackgroundFromBufferParallelFor(ushort[] backgroundBuffer)
{
    Parallel.For(0, Buffer.Length, (i) =>
    {
        int difference = Buffer[i] - backgroundBuffer[i];
        if (difference >= 0)
            Buffer[i] = (ushort)difference;
        else
            Buffer[i] = 0;
    });
}        

public static void SubtractBackgroundFromBufferBlockParallelFor(ushort[] backgroundBuffer)
{
    int blockSize = 4096;

    Parallel.For(0, (int)Math.Ceiling(Buffer.Length / (double)blockSize), (j) =>
    {
        for (int i = j * blockSize; i < (j + 1) * blockSize; i++)
        {
            int difference = Buffer[i] - backgroundBuffer[i];

            Buffer[i] = (ushort)Math.Max(difference, 0);                    
        }
    });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEach(ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
        {
            for (int i = range.Item1; i < range.Item2; ++i)
            {
                if (Buffer[i] < backgroundBuffer[i])
                {
                    Buffer[i] = 0;
                }
                else
                {
                    Buffer[i] -= backgroundBuffer[i];
                }
            }
        });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEachHack(ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
    {
        for (int i = range.Item1; i < range.Item2; ++i)
        {
            unsafe
            {
                var nonNegative = Buffer[i] > backgroundBuffer[i];
                Buffer[i] = (ushort)((Buffer[i] - backgroundBuffer[i]) *
                    *((int*)(&nonNegative)));
            }
        }
    });
}

我在发布模式下为每个方法运行了这个。我以这种方式启动和停止秒表，以确保只测量处理时间

System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
ushort[] bgImg = GenerateRandomBuffer(327680, 818687447);

for (int i = 0; i < 1000; i++)
{
    Buffer = GenerateRandomBuffer(327680, 128011992);                

    sw.Start();
    SubtractBackgroundFromBuffer(bgImg);
    sw.Stop();
}

Console.WriteLine("SubtractBackgroundFromBuffer(ms): " + sw.Elapsed.TotalMilliseconds.ToString("N2"));


public static ushort[] GenerateRandomBuffer(int size, int randomSeed)
{
    ushort[] buffer = new ushort[327680];
    Random random = new Random(randomSeed);

    for (int i = 0; i < size; i++)
    {
        buffer[i] = (ushort)random.Next(ushort.MinValue, ushort.MaxValue);
    }

    return buffer;
}

System.Diagnostics.Stopwatch sw=新的System.Diagnostics.Stopwatch（）；
ushort[]bgImg=GenerateRandomBuffer（327680818687447）；
对于（int i=0；i<1000；i++）
{
Buffer=GenerateRandomBuffer（327680128011992）；
sw.Start（）；
从缓冲区中减去背景（bgImg）；
sw.Stop（）；
}
Console.WriteLine（“SubtractBackgroundFromBuffer（ms）：”+sw.appeased.total毫秒.ToString（“N2”）；
公共静态ushort[]GenerateRandomBuffer（int-size，int-randomSeed）
{
ushort[]buffer=新的ushort[327680]；
随机随机=新随机（随机种子）；
对于（int i=0；i

方法

public static void SubtractBackgroundFromBuffer(ushort[] backgroundBuffer)
{
    int bufferLength = Buffer.Length;

    for (int index = 0; index < bufferLength; index++)
    {
        int difference = Buffer[index] - backgroundBuffer[index];

        if (difference >= 0)
            Buffer[index] = (ushort)difference;
        else
            Buffer[index] = 0;
    }
}

public static void SubtractBackgroundFromBufferWithCalcOpt(ushort[] backgroundBuffer)
{
    int bufferLength = Buffer.Length;

    for (int index = 0; index < bufferLength; index++)
    {
        if (Buffer[index] < backgroundBuffer[index])
        {
            Buffer[index] = 0;
        }
        else
        {
            Buffer[index] -= backgroundBuffer[index];
        }
    }
}

public static void SubtractBackgroundFromBufferParallelFor(ushort[] backgroundBuffer)
{
    Parallel.For(0, Buffer.Length, (i) =>
    {
        int difference = Buffer[i] - backgroundBuffer[i];
        if (difference >= 0)
            Buffer[i] = (ushort)difference;
        else
            Buffer[i] = 0;
    });
}        

public static void SubtractBackgroundFromBufferBlockParallelFor(ushort[] backgroundBuffer)
{
    int blockSize = 4096;

    Parallel.For(0, (int)Math.Ceiling(Buffer.Length / (double)blockSize), (j) =>
    {
        for (int i = j * blockSize; i < (j + 1) * blockSize; i++)
        {
            int difference = Buffer[i] - backgroundBuffer[i];

            Buffer[i] = (ushort)Math.Max(difference, 0);                    
        }
    });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEach(ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
        {
            for (int i = range.Item1; i < range.Item2; ++i)
            {
                if (Buffer[i] < backgroundBuffer[i])
                {
                    Buffer[i] = 0;
                }
                else
                {
                    Buffer[i] -= backgroundBuffer[i];
                }
            }
        });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEachHack(ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
    {
        for (int i = range.Item1; i < range.Item2; ++i)
        {
            unsafe
            {
                var nonNegative = Buffer[i] > backgroundBuffer[i];
                Buffer[i] = (ushort)((Buffer[i] - backgroundBuffer[i]) *
                    *((int*)(&nonNegative)));
            }
        }
    });
}

publicstaticvoid减去backgroundfrombuffer（ushort[]backgroundBuffer）
{
int bufferLength=Buffer.Length；
for（int index=0；index=0）
缓冲区[索引]=（ushort）差异；
其他的
缓冲区[索引]=0；
}
}
公共静态void减去backgroundfromBufferwithCalCopt（ushort[]backgroundBuffer）
{
int bufferLength=Buffer.Length；
for（int index=0；index
{
int差分=缓冲区[i]-背景缓冲区[i]；
如果（差异>=0）
缓冲区[i]=（ushort）差；
其他的
缓冲区[i]=0；
});
}        
public static void SubtractBackgroundFromBufferBlockParallelFor（ushort[]backgroundBuffer）
{
int blockSize=4096；
对于（0，（int）数学上限（Buffer.Length/（double）blockSize），（j）=>
{
对于（int i=j*blockSize；i<（j+1）*blockSize；i++）
{
int差分=缓冲区[i]-背景缓冲区[i]；
缓冲区[i]=（ushort）数学最大值（差，0）；
}
});
}
公共静态void从BufferPartitionedParallelforeach中减去Background（ushort[]backgroundBuffer）
{
Parallel.ForEach（Partitioner.Create（0，Buffer.Length），range=>
{
对于（int i=range.Item1；i
{
对于（int i=range.Item1；i背景缓冲区[i]；
缓冲区[i]=（ushort）（（缓冲区[i]-背景缓冲区[i]）*
*（（int*）（&非负））；
}
}
});
}

这是一个有趣的问题

只执行

public static void SubtractBackgroundFromBuffer(ushort[] backgroundBuffer)
{
    int bufferLength = Buffer.Length;

    for (int index = 0; index < bufferLength; index++)
    {
        int difference = Buffer[index] - backgroundBuffer[index];

        if (difference >= 0)
            Buffer[index] = (ushort)difference;
        else
            Buffer[index] = 0;
    }
}

public static void SubtractBackgroundFromBufferWithCalcOpt(ushort[] backgroundBuffer)
{
    int bufferLength = Buffer.Length;

    for (int index = 0; index < bufferLength; index++)
    {
        if (Buffer[index] < backgroundBuffer[index])
        {
            Buffer[index] = 0;
        }
        else
        {
            Buffer[index] -= backgroundBuffer[index];
        }
    }
}

public static void SubtractBackgroundFromBufferParallelFor(ushort[] backgroundBuffer)
{
    Parallel.For(0, Buffer.Length, (i) =>
    {
        int difference = Buffer[i] - backgroundBuffer[i];
        if (difference >= 0)
            Buffer[i] = (ushort)difference;
        else
            Buffer[i] = 0;
    });
}        

public static void SubtractBackgroundFromBufferBlockParallelFor(ushort[] backgroundBuffer)
{
    int blockSize = 4096;

    Parallel.For(0, (int)Math.Ceiling(Buffer.Length / (double)blockSize), (j) =>
    {
        for (int i = j * blockSize; i < (j + 1) * blockSize; i++)
        {
            int difference = Buffer[i] - backgroundBuffer[i];

            Buffer[i] = (ushort)Math.Max(difference, 0);                    
        }
    });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEach(ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
        {
            for (int i = range.Item1; i < range.Item2; ++i)
            {
                if (Buffer[i] < backgroundBuffer[i])
                {
                    Buffer[i] = 0;
                }
                else
                {
                    Buffer[i] -= backgroundBuffer[i];
                }
            }
        });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEachHack(ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
    {
        for (int i = range.Item1; i < range.Item2; ++i)
        {
            unsafe
            {
                var nonNegative = Buffer[i] > backgroundBuffer[i];
                Buffer[i] = (ushort)((Buffer[i] - backgroundBuffer[i]) *
                    *((int*)(&nonNegative)));
            }
        }
    });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEach(
    ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
        {
            for (int i = range.Item1; i < range.Item2; ++i)
            {
                if (Buffer[i] < backgroundBuffer[i])
                {
                    Buffer[i] = 0;
                }
                else
                {
                    Buffer[i] -= backgroundBuffer[i];
                }
            }
        });
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEachHack(
    ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
        {
            for (int i = range.Item1; i < range.Item2; ++i)
            {
                unsafe
                {
                    var nonNegative = Buffer[i] > backgroundBuffer[i];
                    Buffer[i] = (ushort)((Buffer[i] - backgroundBuffer[i]) *
                        *((int*)(&nonNegative)));
                }
            }
        });
}

UInt16 MyCppLib::Maths::SafeSubtraction(UInt16 minuend, UInt16 subtrahend)
{
    return (UInt16)((minuend - subtrahend) * (minuend > subtrahend));
}

public static void SubtractBackgroundFromBufferPartitionedParallelForEachCpp(
    ushort[] backgroundBuffer)
{
    Parallel.ForEach(Partitioner.Create(0, Buffer.Length), range =>
    {
        for (int i = range.Item1; i < range.Item2; ++i)
        {
            Buffer[i] = 
                MyCppLib.Maths.SafeSubtraction(Buffer[i], backgroundBuffer[i]);
        }
    });
}

1. SubtractBackgroundFromBuffer(ms):                               2,021.37
2. SubtractBackgroundFromBufferWithCalcOpt(ms):                    2,125.80
3. SubtractBackgroundFromBufferParallelFor(ms):                    3,431.58
4. SubtractBackgroundFromBufferBlockParallelFor(ms):               1,401.36
5. SubtractBackgroundFromBufferPartitionedParallelForEach(ms):     1,197.76
6. SubtractBackgroundFromBufferPartitionedParallelForEachHack(ms):   742.72
7. SubtractBackgroundFromBufferPartitionedParallelForEachCpp(ms):    499.27

1. SubtractBackgroundFromBuffer(ms):                                 773.50
2. SubtractBackgroundFromBufferWithCalcOpt(ms):                      915.91
3. SubtractBackgroundFromBufferParallelFor(ms):                    2,458.36
4. SubtractBackgroundFromBufferBlockParallelFor(ms):                 663.76
5. SubtractBackgroundFromBufferPartitionedParallelForEach(ms):       658.05
6. SubtractBackgroundFromBufferPartitionedParallelForEachHack(ms):   762.11
7. SubtractBackgroundFromBufferPartitionedParallelForEachCpp(ms):    494.12

Buffer = Buffer.Zip<ushort, ushort, ushort>(backgroundBuffer, (x, y) =>
{
    return (ushort)Math.Max(0, x - y);
}).ToArray();

Enumerable.Range(0, Buffer.Length).AsParalell().ForAll(i =>
    {
         unsafe
        {
            var nonNegative = Buffer[i] > backgroundBuffer[i];
            Buffer[i] = (ushort)((Buffer[i] - backgroundBuffer[i]) *
                *((int*)(&nonNegative)));
        }
    });