message: PetscParMatrix::MatMultKernel do not scale input since it may be locked
diff: @@ -1698,28 +1698,18 @@ static void MatMultKernel(Mat A,PetscScalar a,Vec X,PetscScalar b,Vec Y,
  }
  if (a != 0.)
  {
  - if (b == 1.)
  + if (b != 0.)
  {
  - ierr = VecScale(X,a); PCHKERRQ(A,ierr);
  + ierr = VecScale(Y,b/a); PCHKERRQ(A,ierr);
  ierr = (*fadd)(A,X,Y,Y); PCHKERRQ(A,ierr);
  - ierr = VecScale(X,1./a); PCHKERRQ(A,ierr);
  - }
  - else if (b != 0.)
  - {
  - ierr = VecScale(X,a); PCHKERRQ(A,ierr);
  - ierr = VecScale(Y,b); PCHKERRQ(A,ierr);
  - ierr = (*fadd)(A,X,Y,Y); PCHKERRQ(A,ierr);
  - ierr = VecScale(X,1./a); PCHKERRQ(A,ierr);
  + ierr = VecScale(Y,a); PCHKERRQ(A,ierr);
  }
  else
  {
  ierr = (*f)(A,X,Y); PCHKERRQ(A,ierr);
  - if (a != 1.)
  - {
  ierr = VecScale(Y,a); PCHKERRQ(A,ierr);
  }
  }
  - }
  else
  {
  if (b == 1.)
  