Actual source code: ex17.c
petsc-3.12.4 2020-02-04
Report Typos and Errors

      2: static char help[] = "Tests the use of MatSolveTranspose().\n\n";

      4:  #include <petscmat.h>

      6: int main(int argc,char **args)
      7: {
      8:   Mat            C,A;
      9:   PetscInt       i,j,m = 5,n = 5,Ii,J;
     11:   PetscScalar    v,five = 5.0,one = 1.0;
     12:   IS             isrow,row,col;
     13:   Vec            x,u,b;
     14:   PetscReal      norm;
     15:   MatFactorInfo  info;

     17:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
     18:   PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);
     19:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);

     21:   MatCreateSeqAIJ(PETSC_COMM_SELF,m*n,m*n,5,NULL,&C);
     22:   MatSetUp(C);

     24:   /* create the matrix for the five point stencil, YET AGAIN*/
     25:   for (i=0; i<m; i++) {
     26:     for (j=0; j<n; j++) {
     27:       v = -1.0;  Ii = j + n*i;
     28:       if (i>0)   {J = Ii - n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
     29:       if (i<m-1) {J = Ii + n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
     30:       if (j>0)   {J = Ii - 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
     31:       if (j<n-1) {J = Ii + 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
     32:       v = 4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES);
     33:     }
     34:   }
     35:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
     36:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

     38:   ISCreateStride(PETSC_COMM_SELF,(m*n)/2,0,2,&isrow);
     39:   MatZeroRowsIS(C,isrow,five,0,0);

     41:   VecCreateSeq(PETSC_COMM_SELF,m*n,&u);
     42:   VecDuplicate(u,&x);
     43:   VecDuplicate(u,&b);
     44:   VecSet(u,one);

     46:   MatMultTranspose(C,u,b);

     48:   /* Set default ordering to be Quotient Minimum Degree; also read
     49:      orderings from the options database */
     50:   MatGetOrdering(C,MATORDERINGQMD,&row,&col);

     52:   MatFactorInfoInitialize(&info);
     53:   MatGetFactor(C,MATSOLVERPETSC,MAT_FACTOR_LU,&A);
     54:   MatLUFactorSymbolic(A,C,row,col,&info);
     55:   MatLUFactorNumeric(A,C,&info);
     56:   MatSolveTranspose(A,b,x);

     58:   ISView(row,PETSC_VIEWER_STDOUT_SELF);
     59:   VecAXPY(x,-1.0,u);
     60:   VecNorm(x,NORM_2,&norm);
     61:   PetscPrintf(PETSC_COMM_SELF,"Norm of error %g\n",(double)norm);

     63:   ISDestroy(&row);
     64:   ISDestroy(&col);
     65:   ISDestroy(&isrow);
     66:   VecDestroy(&u);
     67:   VecDestroy(&x);
     68:   VecDestroy(&b);
     69:   MatDestroy(&C);
     70:   MatDestroy(&A);
     71:   PetscFinalize();
     72:   return ierr;
     73: }

     76: /*TEST

     78:    test:

     80: TEST*/