稀疏矩阵，目前还没有一个明确的定义，但是一般认为，稀疏矩阵是非零元素较零元素少，且分布没有一定规律的矩阵。在矩阵运算中和矩阵输入输出中，最方便的存储方式就是二维数组，对矩阵进行压缩不能简化矩阵运算，对输入输出也不能提供便利，而降低运算的时间复杂度主要与算法有关，一般对矩阵压缩后其运算的复杂度会增加。所以答案是节省存储空间。-Sparse matrix, there is no a clear definition, but is generally believed that non-zero elements of sparse matrix is less than zero elements, and not necessarily the law of the distribution matrix. In the matrix calculation and input-output matrix, the most convenient way to store two-dimensional array of matrix compression can not be simplified matrix calculation on the input and output can not facilitate, and reduce the computing time complexity algorithm primarily related to general matrix compression on the complexity of its operations will increase. So the answer is to save storage space.