Hi dear whoever reads this: I have a quick question: After matrix assembly, suppouse I have matrix A. Assuming I used 16 processors, if I want each processor to print out their local contents of the A, how do I proceed? (I simply want to know how the matrix is stored from generating to communicating to solving, so I get to display all the time to get better undersdtanding) I read the examples, and I tried things like below and sooooo many different codes from examples, it still is not working. PetscViewer viewer; PetscMPIInt my_rank; MPI_Comm_rank(PETSC_COMM_WORLD,&my_rank); PetscPrintf(MPI_COMM_SELF,"[%d] rank\n",my_rank); PetscViewerASCIIOpen(MPI_COMM_SELF,NULL,&viewer); PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_INFO); MatView(impOP,viewer); Plea......se give me some hints Thank you so very much! Longyin Cui (or you know me as Eric); Student from C.S. division; Cell: 7407047169; return 0;