2: static char help[] = "Test MatAXPY(), and illustrate how to reduce number of mallocs used during MatSetValues() calls \n\
  3:                       Matrix C is copied from ~petsc/src/ksp/ksp/examples/tutorials/ex5.c\n\n";
  4: /*
  5:   Example: ./ex132 -mat_view ascii::ascii_info
  6: */

  8:  #include <petscmat.h>

 10: int main(int argc,char **args)
 11: {
 12:   Mat            C,C1,C2;           /* matrix */
 13:   PetscScalar    v;
 14:   PetscInt       Ii,J,Istart,Iend;
 16:   PetscInt       i,j,m = 3,n = 2;
 17:   PetscMPIInt    size,rank;
 18:   PetscBool      mat_nonsymmetric = PETSC_FALSE;
 19:   MatInfo        info;

 21:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
 22:   PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);
 23:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 24:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 25:   n    = 2*size;

 27:   /* Set flag if we are doing a nonsymmetric problem; the default is symmetric. */
 28:   PetscOptionsGetBool(NULL,NULL,"-mat_nonsym",&mat_nonsymmetric,NULL);

 30:   MatCreate(PETSC_COMM_WORLD,&C);
 31:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 32:   MatSetFromOptions(C);
 33:   MatSeqAIJSetPreallocation(C,5,NULL);

 35:   MatGetOwnershipRange(C,&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(C,1,&Ii,1,&J,&v,ADD_VALUES);}
 39:     if (i<m-1) {J = Ii + n; MatSetValues(C,1,&Ii,1,&J,&v,ADD_VALUES);}
 40:     if (j>0)   {J = Ii - 1; MatSetValues(C,1,&Ii,1,&J,&v,ADD_VALUES);}
 41:     if (j<n-1) {J = Ii + 1; MatSetValues(C,1,&Ii,1,&J,&v,ADD_VALUES);}
 42:     v = 4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,ADD_VALUES);
 43:   }

 45:   /* Make the matrix nonsymmetric if desired */
 46:   if (mat_nonsymmetric) {
 47:     for (Ii=Istart; Ii<Iend; Ii++) {
 48:       v = -1.5; i = Ii/n;
 49:       if (i>1)   {J = Ii-n-1; MatSetValues(C,1,&Ii,1,&J,&v,ADD_VALUES);}
 50:     }
 51:   } else {
 52:     MatSetOption(C,MAT_SYMMETRIC,PETSC_TRUE);
 53:     MatSetOption(C,MAT_SYMMETRY_ETERNAL,PETSC_TRUE);
 54:   }
 55:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 56:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

 58:   /* First, create C1 = 2.0*C1 + C, C1 has less non-zeros than C */
 59:   PetscPrintf(PETSC_COMM_WORLD, "\ncreate C1 = 2.0*C1 + C, C1 has less non-zeros than C \n");
 60:   MatCreate(PETSC_COMM_WORLD,&C1);
 61:   MatSetSizes(C1,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 62:   MatSetFromOptions(C1);
 63:   MatSeqAIJSetPreallocation(C1,1,NULL);
 64:   for (Ii=Istart; Ii<Iend; Ii++) {
 65:     MatSetValues(C1,1,&Ii,1,&Ii,&v,ADD_VALUES);
 66:   }
 67:   MatAssemblyBegin(C1,MAT_FINAL_ASSEMBLY);
 68:   MatAssemblyEnd(C1,MAT_FINAL_ASSEMBLY);
 69:   PetscPrintf(PETSC_COMM_WORLD," MatAXPY(C1,2.0,C,DIFFERENT_NONZERO_PATTERN)...\n");
 70:   MatAXPY(C1,2.0,C,DIFFERENT_NONZERO_PATTERN);
 71:   MatGetInfo(C1,MAT_GLOBAL_SUM,&info);
 72:   PetscPrintf(PETSC_COMM_WORLD," C1: nz_allocated = %g; nz_used = %g; nz_unneeded = %g\n",info.nz_allocated,info.nz_used, info.nz_unneeded);

 74:   /* Secondly, create C2 = 2.0*C2 + C, C2 has non-zero pattern of C2 + C */
 75:   PetscPrintf(PETSC_COMM_WORLD, "\ncreate C2 = 2.0*C2 + C, C2 has non-zero pattern of C2 + C \n");
 76:   MatDuplicate(C,MAT_DO_NOT_COPY_VALUES,&C2);

 78:   for (Ii=Istart; Ii<Iend; Ii++) {
 79:     v    = 1.0;
 80:     MatSetValues(C2,1,&Ii,1,&Ii,&v,ADD_VALUES);
 81:   }
 82:   MatAssemblyBegin(C2,MAT_FINAL_ASSEMBLY);
 83:   MatAssemblyEnd(C2,MAT_FINAL_ASSEMBLY);
 84:   PetscPrintf(PETSC_COMM_WORLD," MatAXPY(C2,2.0,C,SUBSET_NONZERO_PATTERN)...\n");
 85:   MatAXPY(C2,2.0,C,SUBSET_NONZERO_PATTERN);
 86:   MatGetInfo(C2,MAT_GLOBAL_SUM,&info);
 87:   PetscPrintf(PETSC_COMM_WORLD," C2: nz_allocated = %g; nz_used = %g; nz_unneeded = %g\n",info.nz_allocated,info.nz_used, info.nz_unneeded);

 89:   MatDestroy(&C1);
 90:   MatDestroy(&C2);
 91:   MatDestroy(&C);

 93:   PetscFinalize();
 94:   return ierr;
 95: }