Actual source code: ex1.c

  2: static char help[] = "Tests solving linear system on 0 by 0 matrix.\n\n";

 4:  #include petscksp.h

  8: int main(int argc,char **args)
  9: {
 10:   Mat            C;
 12:   PetscInt       N = 0;
 13:   Vec            u,b,x;
 14:   KSP            ksp;
 15:   PetscReal      norm;

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

 19:   /* create stiffness matrix */
 20:   MatCreate(PETSC_COMM_SELF,&C);
 21:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,N,N);
 22:   MatSetFromOptions(C);
 23:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 24:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

 26:   /* create right hand side and solution */

 28:   VecCreateSeq(PETSC_COMM_SELF,N,&u);
 29:   VecDuplicate(u,&b);
 30:   VecDuplicate(u,&x);
 31:   VecSet(u,0.0);
 32:   VecSet(b,0.0);

 34:   VecAssemblyBegin(b);
 35:   VecAssemblyEnd(b);


 38:   /* solve linear system */
 39:   KSPCreate(PETSC_COMM_WORLD,&ksp);
 40:   KSPSetOperators(ksp,C,C,DIFFERENT_NONZERO_PATTERN);
 41:   KSPSetFromOptions(ksp);
 42:   KSPSolve(ksp,b,u);

 44:   MatMult(C,u,x);
 45:   VecAXPY(x,-1.0,b);
 46:   VecNorm(x,NORM_2,&norm);

 48:   KSPDestroy(ksp);
 49:   VecDestroy(u);
 50:   VecDestroy(x);
 51:   VecDestroy(b);
 52:   MatDestroy(C);
 53:   PetscFinalize();
 54:   return 0;
 55: }