Actual source code: ex7.c

  1: /*$Id: ex7.c,v 1.20 2001/08/07 21:30:08 bsmith Exp $*/

  3: static char help[] = "Tests matrix factorization.  Note that most users should\n\
  4: employ the KSP  interface to the linear solvers instead of using the factorization\n\
  5: routines directly.\n\n";

 7:  #include petscmat.h

 11: int main(int argc,char **args)
 12: {
 13:   Mat         C,LU;
 14:   MatInfo     info;
 15:   int         i,j,m = 3,n = 3,I,J,ierr;
 16:   PetscScalar v,mone = -1.0,one = 1.0;
 17:   IS          perm,iperm;
 18:   Vec         x,u,b;
 19:   PetscReal   norm;
 20:   MatFactorInfo   luinfo;

 22:   PetscInitialize(&argc,&args,(char *)0,help);

 24:   /* Create the matrix for the five point stencil, YET AGAIN */
 25:   MatCreate(PETSC_COMM_SELF,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n,&C);
 26:   MatSetFromOptions(C);
 27:   for (i=0; i<m; i++) {
 28:     for (j=0; j<n; j++) {
 29:       v = -1.0;  I = j + n*i;
 30:       if (i>0)   {J = I - n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 31:       if (i<m-1) {J = I + n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 32:       if (j>0)   {J = I - 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 33:       if (j<n-1) {J = I + 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 34:       v = 4.0; MatSetValues(C,1,&I,1,&I,&v,INSERT_VALUES);
 35:     }
 36:   }
 37:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 38:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
 39:   MatGetOrdering(C,MATORDERING_RCM,&perm,&iperm);
 40:   MatView(C,PETSC_VIEWER_STDOUT_WORLD);
 41:   ISView(perm,PETSC_VIEWER_STDOUT_SELF);

 43:   luinfo.fill = 2.0;
 44:   luinfo.dtcol = 0.0;
 45:   luinfo.damping = 0.0;
 46:   luinfo.zeropivot = 1.e-14;
 47:   luinfo.pivotinblocks = 1.0;
 48:   MatLUFactorSymbolic(C,perm,iperm,&luinfo,&LU);
 49:   MatLUFactorNumeric(C,&LU);
 50:   MatView(LU,PETSC_VIEWER_STDOUT_WORLD);

 52:   VecCreateSeq(PETSC_COMM_SELF,m*n,&u);
 53:   VecSet(&one,u);
 54:   VecDuplicate(u,&x);
 55:   VecDuplicate(u,&b);

 57:   MatMult(C,u,b);
 58:   MatSolve(LU,b,x);

 60:   VecView(b,PETSC_VIEWER_STDOUT_SELF);
 61:   VecView(x,PETSC_VIEWER_STDOUT_SELF);

 63:   VecAXPY(&mone,u,x);
 64:   VecNorm(x,NORM_2,&norm);
 65:   PetscPrintf(PETSC_COMM_SELF,"Norm of error %A\n",norm);

 67:   MatGetInfo(C,MAT_LOCAL,&info);
 68:   PetscPrintf(PETSC_COMM_SELF,"original matrix nonzeros = %d\n",(int)info.nz_used);
 69:   MatGetInfo(LU,MAT_LOCAL,&info);
 70:   PetscPrintf(PETSC_COMM_SELF,"factored matrix nonzeros = %d\n",(int)info.nz_used);

 72:   VecDestroy(u);
 73:   VecDestroy(b);
 74:   VecDestroy(x);
 75:   ISDestroy(perm);
 76:   ISDestroy(iperm);
 77:   MatDestroy(C);
 78:   MatDestroy(LU);

 80:   PetscFinalize();
 81:   return 0;
 82: }