Actual source code: ex44.c

petsc-3.7.5 2017-01-01
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  2: static char help[] = "Solves a tridiagonal linear system.  Designed to compare SOR for different Mat impls.\n\n";

  4: #include <petscksp.h>

  8: int main(int argc,char **args)
  9: {
 10:   KSP            ksp;      /* linear solver context */
 11:   Mat            A;        /* linear system matrix */
 12:   Vec            x,b;      /* approx solution, RHS */
 13:   PetscInt       Ii,Istart,Iend;
 15:   PetscScalar    v[3] = {-1./2., 1., -1./2.};
 16:   PetscInt       j[3];
 17:   PetscInt       k=15;
 18:   PetscInt       M,m=420;

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

 22:   PetscOptionsGetInt(NULL,NULL,"-k",&k,NULL);
 23:   PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);

 25:   KSPCreate(PETSC_COMM_WORLD,&ksp);
 26:   KSPSetFromOptions(ksp);
 27:   KSPGetOperators(ksp,&A,NULL);

 29:   MatSetSizes(A,m,m,PETSC_DETERMINE,PETSC_DETERMINE);
 30:   MatSetFromOptions(A);
 31:   MatSetUp(A);
 32:   MatGetOwnershipRange(A,&Istart,&Iend);
 33:   MatGetSize(A,&M,NULL);
 34:   for (Ii=Istart; Ii<Iend; Ii++) {
 35:     j[0] = Ii - k;
 36:     j[1] = Ii;
 37:     j[2] = (Ii + k) < M ? (Ii + k) : -1;
 38:     MatSetValues(A,1,&Ii,3,j,v,INSERT_VALUES);
 39:   }
 40:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 41:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
 42:   MatCreateVecs(A,&x,&b);

 44:   VecSetFromOptions(b);
 45:   VecSet(b,1.0);
 46:   VecSetFromOptions(x);
 47:   VecSet(x,2.0);

 49:   KSPSolve(ksp,b,x);

 51:   VecDestroy(&b);
 52:   VecDestroy(&x);
 53:   KSPDestroy(&ksp);

 55:   PetscFinalize();
 56:   return 0;
 57: }