C# 使用Vector256写了一个简单的帮助类Vector256Helper

 当数据量大的时候用普通代码计算非常耗时，这里简单利用simd加速处理

 internal unsafe class Vector256Helper
    {
        /// <summary>
        /// 统计元素个数
        /// </summary>
        /// <param name="array"></param>
        /// <param name="elementToCount">需要统计的元素</param>
        /// <returns></returns>
        public static int Count(int[] array, int elementToCount)
        {
            int count = 0;
            int vectorSize = Vector256<int>.Count;
            int limit = array.Length - (array.Length % vectorSize);
            fixed (int* pArray = array)
            {
                int* ptr = pArray;
                var target = Vector256.Create(elementToCount);
                Vector256<int> equalMask = Vector256<int>.Zero;
                for (int i = 0; i < limit; i += vectorSize)
                {
                    Vector256<int> vector = *(Vector256<int>*)(ptr + i);
                    equalMask += Avx2.CompareEqual(vector, target);
                }
                int* equalMaskPtr = (int*)&equalMask;
                for (int j = 0; j < vectorSize; j++)
                {
                    count += -*(equalMaskPtr + j);
                }
                // 处理剩余的元素
                for (int i = limit; i < array.Length; i++)
                {
                    if (*(pArray + i) == elementToCount)
                        count++;
                }
            }
            return count;
        }
        /// <summary>
        /// 求和
        /// </summary>
        /// <param name="buffer"