Hi, guys, I'm trying to solve a linear system with M equations and N unknowns (M >> N) using the LSQR method. I have a C parallel sparse matrix MxN with NZ nonzero elements stored in this way: double values[NZ]; // the nonzero values int idxn[NZ]; // the column indices int nz[M]; // the number of nonzero values for each row what is the best way to create a PETSc matrix? Do exists a statement like VecCreateMPIWithArray for already distributed vectors that could do all the work in one shot without copy? Just another detail. Initially M is unknown. All my structures are allocated dynamically because the number of rows M (and the number of nonzero NZ also) is determined just before to solve the system, so I think it's no feasible for me to call MatCreateMPIAIJ at the begin of my code and to perform the MatSetValues loop. Roberto ================================================================ | Roberto Gori CINECA | High Performance System Group Via Magnanelli 6/3 40033 | e-mail: [email protected] Casalecchio di Reno | Tel: 051/6171522 Bologna - ITALY | Fax: 051/6132198 http://www.cineca.it ================================================================