Actual source code: ex185.c

petsc-3.12.1 2019-10-22
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  1: static char help[] = "Tests MatCreateConstantDiagonal().\n"
  2: "\n";

  4:  #include <petscmat.h>

  6: /*T
  7:     Concepts: Mat
  8: T*/

 10: int main(int argc, char **args)
 11: {
 13:   Vec            X, Y;
 14:   Mat            A,Af;
 15:   PetscReal      xnorm,ynorm;

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

 19:   MatCreateConstantDiagonal(PETSC_COMM_WORLD,PETSC_DETERMINE,PETSC_DETERMINE,20,20,3.0,&A);
 20:   MatCreateVecs(A,&X,&Y);
 21:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);

 23:   VecSetRandom(X,NULL);
 24:   VecNorm(X,NORM_2,&xnorm);
 25:   MatMult(A,X,Y);
 26:   VecNorm(Y,NORM_2,&ynorm);
 27:   if (PetscAbsReal(ynorm - 3*xnorm) > PETSC_SMALL) SETERRQ2(PETSC_COMM_WORLD,PETSC_ERR_PLIB,"Expected norm %g actual norm %g\n",(double)3*xnorm,(double)ynorm);
 28:   MatShift(A,5.0);
 29:   MatScale(A,.5);
 30:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
 31:   MatGetDiagonal(A,Y);

 33:   MatGetFactor(A,MATSOLVERPETSC,MAT_FACTOR_LU,&Af);
 34:   MatLUFactorSymbolic(Af,A,NULL,NULL,NULL);
 35:   MatLUFactorNumeric(Af,A,NULL);
 36:   MatSolve(Af,X,Y);
 37:   VecNorm(Y,NORM_2,&ynorm);
 38:   if (PetscAbsReal(ynorm - xnorm/4) > PETSC_SMALL) SETERRQ2(PETSC_COMM_WORLD,PETSC_ERR_PLIB,"Expected norm %g actual norm %g\n",(double).25*xnorm,(double)ynorm);

 40:   MatDestroy(&A);
 41:   MatDestroy(&Af);
 42:   VecDestroy(&X);
 43:   VecDestroy(&Y);

 45:   PetscFinalize();
 46:   return ierr;
 47: }

 49: /*TEST

 51:   test:
 52:     nsize: 2

 54: TEST*/