Sure. Thanks for your information. Actually, I used to call MatSetValues for each column. Since my matrix is sparse and I am not sure whether the non-zeros along each column are identical for each row, I am currently wondering if it is possible to insert the entire local dense matrix into the global sparse matrix using a single MatSetValues routine. Would it be more efficient than I identify the nonzeros and inserting them row-by-row? I may also set the “IGNORE_ZERO_ENTRIES” for the global sparse matrix before “MatSetValues”. Would it be helpful? Thanks for your helps.
From: Matthew Knepley [mailto:[email protected]] Sent: Wednesday, 15 April 2020 7:01 PM To: Bin Liu <[email protected]> Cc: Junchao Zhang <[email protected]>; [email protected] Subject: Re: [petsc-users] inserting multiple rows together into a matrix On Wed, Apr 15, 2020 at 1:24 AM Bin Liu <[email protected]<mailto:[email protected]>> wrote: Thanks for your example. My problem is resolved. Meanwhile I am wondering, if it is possible to make this example more flexible. I mean what if the columns in each row are different? Is there any way to insert them all together? No. If the columns are different, you make a separate calls to MatSetValues(). Thanks, Matt Regards Bin From: Junchao Zhang [mailto:[email protected]<mailto:[email protected]>] Sent: Monday, 13 April 2020 11:33 PM To: Bin Liu <[email protected]<mailto:[email protected]>> Cc: [email protected]<mailto:[email protected]> Subject: Re: [petsc-users] inserting multiple rows together into a matrix Add two rows 2 ,4, and each row has three nonzeros at column 3, 7, 9 m=2; n=3; idxm[] = {2, 4}; idxn[] = {3, 7, 9}; v[6] = {0.1, 0.2, ....}; MatSetValues(mat, m, idxm, n, idxn,v, INSERT_VALUES); --Junchao Zhang On Mon, Apr 13, 2020 at 9:59 AM Bin Liu <[email protected]<mailto:[email protected]>> wrote: Hi all, I know how to insert values in one row into the matrix via routine “MatSetValues”. I understand I logically should be able to insert multiple rows into the matrix with one call of “MatSetValues”. However, I am not sure how to do it. I searched in the PETSc mail list and did not find a relevant question answered before. Could anyone help me and give me a simple example code? Regards B. -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener https://www.cse.buffalo.edu/~knepley/<http://www.cse.buffalo.edu/~knepley/>
