xref: /petsc/src/mat/tutorials/ex8.c (revision 40badf4fbc550ac1f60bd080eaff6de6d55b946d)
1 
2 static char help[] = "Shows how to add a new MatOperation to AIJ MatType\n\n";
3 
4 #include <petscmat.h>
5 #include <petscblaslapack.h>
6 
7 static PetscErrorCode MatScaleUserImpl_SeqAIJ(Mat inA,PetscScalar alpha)
8 {
9   PetscFunctionBegin;
10   CHKERRQ(MatScale(inA,alpha));
11   PetscFunctionReturn(0);
12 }
13 
14 extern PetscErrorCode MatScaleUserImpl(Mat,PetscScalar);
15 
16 static PetscErrorCode MatScaleUserImpl_MPIAIJ(Mat A,PetscScalar aa)
17 {
18   Mat            AA,AB;
19 
20   PetscFunctionBegin;
21   CHKERRQ(MatMPIAIJGetSeqAIJ(A,&AA,&AB,NULL));
22   CHKERRQ(MatScaleUserImpl(AA,aa));
23   CHKERRQ(MatScaleUserImpl(AB,aa));
24   PetscFunctionReturn(0);
25 }
26 
27 /* This routine registers MatScaleUserImpl_SeqAIJ() and
28    MatScaleUserImpl_MPIAIJ() as methods providing MatScaleUserImpl()
29    functionality for SeqAIJ and MPIAIJ matrix-types */
30 PetscErrorCode RegisterMatScaleUserImpl(Mat mat)
31 {
32   PetscMPIInt    size;
33 
34   PetscFunctionBegin;
35   CHKERRMPI(MPI_Comm_size(PetscObjectComm((PetscObject)mat), &size));
36   if (size == 1) { /* SeqAIJ Matrix */
37     CHKERRQ(PetscObjectComposeFunction((PetscObject)mat,"MatScaleUserImpl_C",MatScaleUserImpl_SeqAIJ));
38   } else { /* MPIAIJ Matrix */
39     Mat AA,AB;
40     CHKERRQ(MatMPIAIJGetSeqAIJ(mat,&AA,&AB,NULL));
41     CHKERRQ(PetscObjectComposeFunction((PetscObject)mat,"MatScaleUserImpl_C",MatScaleUserImpl_MPIAIJ));
42     CHKERRQ(PetscObjectComposeFunction((PetscObject)AA,"MatScaleUserImpl_C",MatScaleUserImpl_SeqAIJ));
43     CHKERRQ(PetscObjectComposeFunction((PetscObject)AB,"MatScaleUserImpl_C",MatScaleUserImpl_SeqAIJ));
44   }
45   PetscFunctionReturn(0);
46 }
47 
48 /* this routines queries the already registered MatScaleUserImp_XXX
49    implementations for the given matrix, and calls the correct
50    routine. i.e if MatType is SeqAIJ, MatScaleUserImpl_SeqAIJ() gets
51    called, and if MatType is MPIAIJ, MatScaleUserImpl_MPIAIJ() gets
52    called */
53 PetscErrorCode MatScaleUserImpl(Mat mat,PetscScalar a)
54 {
55   PetscErrorCode (*f)(Mat,PetscScalar);
56 
57   PetscFunctionBegin;
58   CHKERRQ(PetscObjectQueryFunction((PetscObject)mat,"MatScaleUserImpl_C",&f));
59   if (f) CHKERRQ((*f)(mat,a));
60   PetscFunctionReturn(0);
61 }
62 
63 /* Main user code that uses MatScaleUserImpl() */
64 
65 int main(int argc,char **args)
66 {
67   Mat            mat;
68   PetscInt       i,j,m = 2,n,Ii,J;
69   PetscErrorCode ierr;
70   PetscScalar    v,none = -1.0;
71   PetscMPIInt    rank,size;
72 
73   ierr = PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
74   CHKERRMPI(MPI_Comm_rank(PETSC_COMM_WORLD,&rank));
75   CHKERRMPI(MPI_Comm_size(PETSC_COMM_WORLD,&size));
76   n    = 2*size;
77 
78   /* create the matrix */
79   CHKERRQ(MatCreate(PETSC_COMM_WORLD,&mat));
80   CHKERRQ(MatSetSizes(mat,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n));
81   CHKERRQ(MatSetType(mat,MATAIJ));
82   CHKERRQ(MatSetUp(mat));
83 
84   /* register user defined MatScaleUser() operation for both SeqAIJ
85      and MPIAIJ types */
86   CHKERRQ(RegisterMatScaleUserImpl(mat));
87 
88   /* assemble the matrix */
89   for (i=0; i<m; i++) {
90     for (j=2*rank; j<2*rank+2; j++) {
91       v = -1.0;  Ii = j + n*i;
92       if (i>0)   {J = Ii - n; CHKERRQ(MatSetValues(mat,1,&Ii,1,&J,&v,INSERT_VALUES));}
93       if (i<m-1) {J = Ii + n; CHKERRQ(MatSetValues(mat,1,&Ii,1,&J,&v,INSERT_VALUES));}
94       if (j>0)   {J = Ii - 1; CHKERRQ(MatSetValues(mat,1,&Ii,1,&J,&v,INSERT_VALUES));}
95       if (j<n-1) {J = Ii + 1; CHKERRQ(MatSetValues(mat,1,&Ii,1,&J,&v,INSERT_VALUES));}
96       v = 4.0; CHKERRQ(MatSetValues(mat,1,&Ii,1,&Ii,&v,INSERT_VALUES));
97     }
98   }
99   CHKERRQ(MatAssemblyBegin(mat,MAT_FINAL_ASSEMBLY));
100   CHKERRQ(MatAssemblyEnd(mat,MAT_FINAL_ASSEMBLY));
101 
102   /* check the matrix before and after scaling by -1.0 */
103   CHKERRQ(PetscPrintf(PETSC_COMM_WORLD,"Matrix _before_ MatScaleUserImpl() operation\n"));
104   CHKERRQ(MatView(mat,PETSC_VIEWER_STDOUT_WORLD));
105   CHKERRQ(MatScaleUserImpl(mat,none));
106   CHKERRQ(PetscPrintf(PETSC_COMM_WORLD,"Matrix _after_ MatScaleUserImpl() operation\n"));
107   CHKERRQ(MatView(mat,PETSC_VIEWER_STDOUT_WORLD));
108 
109   CHKERRQ(MatDestroy(&mat));
110   ierr = PetscFinalize();
111   return ierr;
112 }
113 
114 /*TEST
115 
116    test:
117 
118    test:
119       suffix: 2
120       nsize: 2
121 
122 TEST*/
123