1: /*
  2:  * ex195.c
  3:  *
  4:  *  Created on: Aug 24, 2015
  5:  *      Author: Fande Kong <fdkong.jd@gmail.com>
  6:  */

  8: static char help[] = " Demonstrate the use of MatConvert_Nest_AIJ\n";

 10:  #include <petscmat.h>


 13: int main(int argc,char **args)
 14: {
 15:   Mat                 A1,A2,A3,A4,nest;
 16:   Mat                 mata[4];
 17:   Mat                 aij;
 18:   MPI_Comm            comm;
 19:   PetscInt            m,n,istart,iend,ii,i,J,j;
 20:   PetscScalar         v;
 21:   PetscMPIInt         size;
 22:   PetscErrorCode      ierr;

 24:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
 25:   comm = PETSC_COMM_WORLD;
 26:   MPI_Comm_size(comm,&size);
 27:   /*
 28:      Assemble the matrix for the five point stencil, YET AGAIN
 29:   */
 30:   MatCreate(comm,&A1);
 31:   m=2,n=2;
 32:   MatSetSizes(A1,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 33:   MatSetFromOptions(A1);
 34:   MatSetUp(A1);
 35:   MatGetOwnershipRange(A1,&istart,&iend);
 36:   for (ii=istart; ii<iend; ii++) {
 37:     v = -1.0; i = ii/n; j = ii - i*n;
 38:     if (i>0)   {J = ii - n; MatSetValues(A1,1,&ii,1,&J,&v,INSERT_VALUES);}
 39:     if (i<m-1) {J = ii + n; MatSetValues(A1,1,&ii,1,&J,&v,INSERT_VALUES);}
 40:     if (j>0)   {J = ii - 1; MatSetValues(A1,1,&ii,1,&J,&v,INSERT_VALUES);}
 41:     if (j<n-1) {J = ii + 1; MatSetValues(A1,1,&ii,1,&J,&v,INSERT_VALUES);}
 42:     v = 4.0; MatSetValues(A1,1,&ii,1,&ii,&v,INSERT_VALUES);
 43:   }
 44:   MatAssemblyBegin(A1,MAT_FINAL_ASSEMBLY);
 45:   MatAssemblyEnd(A1,MAT_FINAL_ASSEMBLY);
 46:   MatView(A1,PETSC_VIEWER_STDOUT_WORLD);
 47:   MatDuplicate(A1,MAT_COPY_VALUES,&A2);
 48:   MatDuplicate(A1,MAT_COPY_VALUES,&A3);
 49:   MatDuplicate(A1,MAT_COPY_VALUES,&A4);
 50:   /*create a nest matrix */
 51:   MatCreate(comm,&nest);
 52:   MatSetType(nest,MATNEST);
 53:   mata[0]=A1,mata[1]=A2,mata[2]=A3,mata[3]=A4;
 54:   MatNestSetSubMats(nest,2,NULL,2,NULL,mata);
 55:   MatSetUp(nest);
 56:   MatConvert(nest,MATAIJ,MAT_INITIAL_MATRIX,&aij);
 57:   MatView(aij,PETSC_VIEWER_STDOUT_WORLD);
 58:   MatDestroy(&nest);
 59:   MatDestroy(&aij);
 60:   MatDestroy(&A1);
 61:   MatDestroy(&A2);
 62:   MatDestroy(&A3);
 63:   MatDestroy(&A4);
 64:   PetscFinalize();
 65:   return ierr;
 66: }


 69: /*TEST

 71:    test:
 72:       nsize: 2

 74: TEST*/