Just to clarify my observations on serial and parallel discrepancy- The
value from case 1 remains same for serial and parallel, while case 2 gives
different values for serial and parallel.
On Friday, December 1, 2017 at 3:39:20 PM UTC-6, Sambit Das wrote:
>
> Hi All,
>
> I have reduced my bug to the following minimal example: I create a
> MatrixFree object for two different ConstraintMatrices (provided as vector
> of ConstraintMatrices to the reinit(..)).
>
> matrix_free_data.reinit(dofHandlerVector, d_constraintsVector,
> quadratureVector, additional_data);
>
> The dofHandlers are the same for both the ConstraintMatrices. Only
> difference- the first ConstraintMatrix has periodic constraints while the
> second one has no constraints. Next I run two cases
>
> * Case1: *
>
> FEEvaluation<3,FEOrder,FEOrder+1,1> phiTotEval(matrix_free_data,0, 0);
> const unsigned int
> numSubCells=matrix_free_data.n_components_filled(cell);
> const int numQuadPoints=phiTotEval.n_q_points;
>
> double phiTotRhoOutQuadSum=0.0;
> for (unsigned int cell=0; cell<matrix_free_data.n_macro_cells(); ++cell){
>
> phiTotEval.reinit(cell);
> phiTotEval.read_dof_values_plain(dftPtr->poissonPtr->phiTotRhoOut);
> //phiTotRhoOut is a parallel::distributed::Vector where I have previously
> called ConstraintMatrix(the one with periodic constraints)::distribute()
> and update_ghost_values()
>
> // I have also called
> matrix_free_data.initialize_dof_vector(phiTotRhoOut) prior
> phiTotEval.evaluate(true,true);
>
> for (unsigned int q=0; q<numQuadPoints; ++q){
> VectorizedArray<double> phiTot_q= phiTotEval.get_value(q);
>
> for (unsigned int iSubCell=0; iSubCell<numSubCells; ++iSubCell){
> phiTotRhoOutQuadSum+=phiTot_q[iSubCell];
> }
> }
> }
>
> double phiTotRhoOutQuadSumTotal=Utilities::MPI::sum(phiTotRhoOutQuadSum,
> mpi_communicator);
>
> if (this_mpi_process == 0){
> std::cout << "phiTotRhoOutQuadSumTotal_vectorized " <<
> phiTotRhoOutQuadSumTotal<<std::endl;
> }
>
>
> * Case2: *
> Same as Case 1- only first line is changed to (The only difference in
> both cases is the fe_id argument to FEEvaluation constructor)
> FEEvaluation<3,FEOrder,FEOrder+1,1> phiTotEval(matrix_free_data,1, 0);
>
>
>
> I get different values of phiTotRhoOutQuadSumTotal for the two cases when
> run on multiple processors but same value when run on single processor.
> Comparing with a non-vectorized loop, case 1 which uses the periodic
> constraints gives the correct answer. However going by the manual, I
> expected the same value as I am using read_dof_values_plain(..) which
> doesn't take any constraints into account. I am wondering if I am doing
> anything wrong here.
>
> Best,
> Sambit
>
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