问题
I want to implement a matrix-vector multiplication in C. My matrix is 1000 * 1000^2 and highly sparse (less than 0.01% non-zero elements). The non-zero elements are dispersed among the rows (between 0 to 126 non-zero elements per row).
I have heard that generally, using parallel processing for sparse matrix-vector multiplication is challenging and not as efficient as dense matrices because the ratio of computation to memory access is low (Here). But I cannot really understand what is the main difference between a sparse and a dense matrix with respect to parallel computation that makes sparse matrices less efficient.It seems the same problem is still around for the dense matrices (please correct me if I am wrong).
It is appreciated if let me know how dense matrices differ from sparse matrices in terms of parallel processing. Thanks
来源：https://stackoverflow.com/questions/14591879/matrix-vector-multiplication-sparse-vs-dense-matrices