C++ DistMatrix::Grid方法代码示例

inline void outer_panel_mixed_gemm_impl_nn(
        const double alpha,
        const SpParMat<index_type, value_type, SpDCCols<index_type, value_type> > &A,
        const El::DistMatrix<value_type, El::STAR, El::STAR> &S,
        const double beta,
        El::DistMatrix<value_type, col_d, El::STAR> &C) {

    utility::combblas_slab_view_t<index_type, value_type> cbview(A, false);

    //FIXME: factor
    size_t slab_size = 2 * C.Grid().Height();
    for(size_t cur_row_idx = 0; cur_row_idx < cbview.nrows();
        cur_row_idx += slab_size) {

        size_t cur_slab_size =
            std::min(slab_size, cbview.nrows() - cur_row_idx);

        // get the next slab_size columns of B
        El::DistMatrix<value_type, col_d, El::STAR>
            A_row(cur_slab_size, S.Height());

        cbview.extract_elemental_row_slab_view(A_row, cur_slab_size);

        // assemble the distributed column vector
        for(size_t l_col_idx = 0; l_col_idx < A_row.LocalWidth();
            l_col_idx++) {

            size_t g_col_idx = l_col_idx * A_row.RowStride()
                               + A_row.RowShift();

            for(size_t l_row_idx = 0; l_row_idx < A_row.LocalHeight();
                ++l_row_idx) {

                size_t g_row_idx = l_row_idx * A_row.ColStride()
                                   + A_row.ColShift() + cur_row_idx;

                A_row.SetLocal(l_row_idx, l_col_idx,
                               cbview(g_row_idx, g_col_idx));
            }
        }

        El::DistMatrix<value_type, col_d, El::STAR>
            C_slice(cur_slab_size, C.Width());
        El::View(C_slice, C, cur_row_idx, 0, cur_slab_size, C.Width());
        El::LocalGemm(El::NORMAL, El::NORMAL, alpha, A_row, S,
                        beta, C_slice);
    }
}

inline void Gemv(El::Orientation oA,
    T alpha, const El::DistMatrix<T, El::VC, El::STAR>& A,
    const El::DistMatrix<T, El::VC, El::STAR>& x,
    T beta, El::DistMatrix<T, El::STAR, El::STAR>& y) {
    // TODO verify sizes etc.
    // TODO verify matching grids.

    if (oA == El::TRANSPOSE) {
        boost::mpi::communicator comm(y.Grid().Comm().comm,
            boost::mpi::comm_attach);
        El::Matrix<T> ylocal(y.Matrix());
        El::Gemv(El::TRANSPOSE,
            alpha, A.LockedMatrix(), x.LockedMatrix(),
            beta / T(comm.size()), ylocal);
        boost::mpi::all_reduce(comm,
            ylocal.Buffer(), ylocal.MemorySize(), y.Buffer(),
            std::plus<T>());
    } else {
        SKYLARK_THROW_EXCEPTION(base::unsupported_base_operation());
    }
}

index_type owner(const El::DistMatrix<value_type, El::VC, El::STAR> &A,
                 const index_type row_idx, const index_type col_idx) {

    return row_idx % (A.Grid().Height() * A.Grid().Width());
}

inline void outer_panel_mixed_gemm_impl_tn(
        const double alpha,
        const SpParMat<index_type, value_type, SpDCCols<index_type, value_type> > &A,
        const El::DistMatrix<value_type, col_d, El::STAR> &S,
        const double beta,
        El::DistMatrix<value_type, El::STAR, El::STAR> &C) {

    El::DistMatrix<value_type, El::STAR, El::STAR>
        tmp_C(C.Height(), C.Width());
    El::Zero(tmp_C);

    utility::combblas_slab_view_t<index_type, value_type> cbview(A, false);

    //FIXME: factor
    size_t slab_size = 2 * S.Grid().Height();
    for(size_t cur_row_idx = 0; cur_row_idx < cbview.ncols();
        cur_row_idx += slab_size) {

        size_t cur_slab_size =
            std::min(slab_size, cbview.ncols() - cur_row_idx);

        // get the next slab_size columns of B
        El::DistMatrix<value_type, El::STAR, El::STAR>
            A_row(cur_slab_size, S.Height());

        // transpose is column
        //cbview.extract_elemental_column_slab_view(A_row, cur_slab_size);
        cbview.extract_full_slab_view(cur_slab_size);

        // matrix mult (FIXME only iter nz)
        for(size_t l_row_idx = 0; l_row_idx < A_row.LocalHeight();
            ++l_row_idx) {

            size_t g_row_idx = l_row_idx * A_row.ColStride()
                               + A_row.ColShift() + cur_row_idx;

            for(size_t l_col_idx = 0; l_col_idx < A_row.LocalWidth();
                l_col_idx++) {

                //XXX: should be the same as l_col_idx
                size_t g_col_idx = l_col_idx * A_row.RowStride()
                                   + A_row.RowShift();

                // continue if we don't own values in S in this row
                if(!S.IsLocalRow(g_col_idx))
                    continue;

                //get transposed value
                value_type val = alpha * cbview(g_col_idx, g_row_idx);

                for(size_t s_col_idx = 0; s_col_idx < S.LocalWidth();
                    s_col_idx++) {

                    tmp_C.UpdateLocal(g_row_idx, s_col_idx,
                                val * S.GetLocal(S.LocalRow(g_col_idx), s_col_idx));
                }
            }
        }
    }

    //FIXME: scaling
    if(A.getcommgrid()->GetRank() == 0) {
        for(size_t col_idx = 0; col_idx < C.Width(); col_idx++)
            for(size_t row_idx = 0; row_idx < C.Height(); row_idx++)
                tmp_C.UpdateLocal(row_idx, col_idx,
                        beta * C.GetLocal(row_idx, col_idx));
    }

    //FIXME: Use utility getter
    boost::mpi::communicator world(
            A.getcommgrid()->GetWorld(), boost::mpi::comm_duplicate);
    boost::mpi::all_reduce (world,
                        tmp_C.LockedBuffer(),
                        C.Height() * C.Width(),
                        C.Buffer(),
                        std::plus<value_type>());
}

int elemental2vec(const El::DistMatrix<El::Complex<double>,El::VC,El::STAR> &Y, std::vector<double> &vec){
	
	assert((Y.DistData().colDist == El::STAR) and (Y.DistData().rowDist == El::VC));

	int data_dof=2;
	int SCAL_EXP = 1;

	//double *pt_array,*pt_perm_array;
	int r,q,ll,rq; // el vec info
	int nbigs; //Number of large recv (i.e. recv 1 extra data point)
	int pstart; // p_id of nstart
	int rank = El::mpi::WorldRank(); //p_id
	int recv_size; // base recv size
	bool print = (rank == -1); 

	// Get el vec info
	ll = Y.Height();
	const El::Grid* g = &(Y.Grid());
	r = g->Height();
	q = g->Width();
	MPI_Comm comm = (g->Comm()).comm;

	int cheb_deg = InvMedTree<FMM_Mat_t>::cheb_deg;
	int omp_p=omp_get_max_threads();
	size_t n_coeff3=(cheb_deg+1)*(cheb_deg+2)*(cheb_deg+3)/6;
	
	// Get petsc vec params
	//VecGetLocalSize(pt_vec,&nlocal);
	int nlocal = (vec.size())/data_dof;
	if(print) std::cout << "m: " << std::endl;
	int nstart = 0;
	//VecGetArray(pt_vec,&pt_array);
	//VecGetOwnershipRange(pt_vec,&nstart,NULL);
	MPI_Exscan(&nlocal,&nstart,1,MPI_INT,MPI_SUM,comm);

	// Determine who owns the first element we want
	rq = r * q;
	pstart = nstart % rq;
	nbigs = nlocal % rq;
	recv_size = nlocal / rq;
	
	if(print){
		std::cout << "r: " << r << " q: " << q <<std::endl;
		std::cout << "nstart: " << nstart << std::endl;
		std::cout << "ps: " << pstart << std::endl;
		std::cout << "nbigs: " << nbigs << std::endl;
		std::cout << "recv_size: " << recv_size << std::endl;
	}

	// Make recv sizes
	std::vector<int> recv_lengths(rq);
	std::fill(recv_lengths.begin(),recv_lengths.end(),recv_size);
	if(nbigs >0){
		for(int i=0;i<nbigs;i++){
			recv_lengths[(pstart + i) % rq] += 1;
		}
	}

	// Make recv disps
	std::vector<int> recv_disps = exscan(recv_lengths);

	// All2all to get send sizes
	std::vector<int> send_lengths(rq);
	MPI_Alltoall(&recv_lengths[0], 1, MPI_INT, &send_lengths[0], 1, MPI_INT,comm);

	// Scan to get send_disps
	std::vector<int> send_disps = exscan(send_lengths);

	// Do all2allv to get data on correct processor
	std::vector<El::Complex<double>> recv_data(nlocal);
	std::vector<El::Complex<double>> recv_data_ordered(nlocal);
	//MPI_Alltoallv(el_vec.Buffer(),&send_lengths[0],&send_disps[0],MPI_DOUBLE, \
			&recv_data[0],&recv_lengths[0],&recv_disps[0],MPI_DOUBLE,comm);
	El::mpi::AllToAll(Y.LockedBuffer(), &send_lengths[0], &send_disps[0], &recv_data[0],&recv_lengths[0],&recv_disps[0],comm);
	
	if(print){
		//std::cout << "Send data: " <<std::endl << *el_vec.Buffer() <<std::endl;
		std::cout << "Send lengths: " <<std::endl << send_lengths <<std::endl;
		std::cout << "Send disps: " <<std::endl << send_disps <<std::endl;
		std::cout << "Recv data: " <<std::endl << recv_data <<std::endl;
		std::cout << "Recv lengths: " <<std::endl << recv_lengths <<std::endl;
		std::cout << "Recv disps: " <<std::endl << recv_disps <<std::endl;
	}
	
	// Reorder the data so taht it is in the right order for the fmm tree
	for(int p=0;p<rq;p++){
		int base_idx = (p - pstart + rq) % rq;
		int offset = recv_disps[p];
		for(int i=0;i<recv_lengths[p];i++){
			recv_data_ordered[base_idx + rq*i] = recv_data[offset + i];
		}
	}

	// loop through and put the data into the vector
	#pragma omp parallel for
	for(int i=0;i<nlocal; i++){
		vec[2*i] = El::RealPart(recv_data_ordered[i]);
		vec[2*i+1] = El::ImagPart(recv_data_ordered[i]);
	}

//.........这里部分代码省略.........

int vec2elemental(const std::vector<double> &vec, El::DistMatrix<El::Complex<double>,El::VC,El::STAR> &Y){

	int data_dof=2;
	int SCAL_EXP = 1;

	int nlocal,gsize; //local elements, start p_id, global size
	double *pt_array; // will hold local array
	int r,q,rq; //Grid sizes
	int nbigs; //Number of large sends (i.e. send 1 extra data point)
	int pstart; // p_id of nstart
	int rank = El::mpi::WorldRank(); //p_id
	int send_size; // base send size
	bool print = rank == -1; 


	// Get Grid and associated params
	const El::Grid* g = &(Y.Grid());
	r = g->Height();
	q = g->Width();
	MPI_Comm comm = (g->Comm()).comm;

	// Get sizes, array in petsc 
	nlocal = vec.size()/data_dof;
	int nstart = 0;
	MPI_Exscan(&nlocal,&nstart,1,MPI_INT,MPI_SUM,comm);
	//VecGetOwnershipRange(pt_vec,&nstart,NULL);

	//Find processor that nstart belongs to, number of larger sends
	rq = r * q;
	pstart = nstart % rq; //int div
	nbigs = nlocal % rq;
	send_size = nlocal/rq;
	
	if(print){
		std::cout << "r: " << r << " q: " << q <<std::endl;
		std::cout << "nstart: " << nstart << std::endl;
		std::cout << "ps: " << pstart << std::endl;
		std::cout << "nbigs: " << nbigs << std::endl;
		std::cout << "send_size: " << send_size << std::endl;
	}

	// Make send_lengths
	std::vector<int> send_lengths(rq);
	std::fill(send_lengths.begin(),send_lengths.end(),send_size);
	if(nbigs >0){
		for(int j=0;j<nbigs;j++){
			send_lengths[(pstart + j) % rq] += 1;
		}
	}

	// Make send_disps
	std::vector<int> send_disps = exscan(send_lengths);

	std::vector<El::Complex<double>> indata(nlocal);
	// copy the data from an ffm tree to into a local vec of complex data for sending #pragma omp parallel for
	El::Complex<double> val;
	for(int i=0;i<nlocal;i++){
		El::SetRealPart(val,vec[2*i+0]);
		El::SetImagPart(val,vec[2*i+1]);
		indata[i] = val;
	}


	// Make send_dataA, i.e. reorder the data
	std::vector<El::Complex<double>> send_data(nlocal);
	for(int proc=0;proc<rq;proc++){
		int offset = send_disps[proc];
		int base_idx = (proc - pstart + rq) % rq; 
		for(int j=0; j<send_lengths[proc]; j++){
			int idx = base_idx + (j * rq);
			send_data[offset + j] = indata[idx];
		}
	}

	// Do all2all to get recv_lengths
	std::vector<int> recv_lengths(rq);
	MPI_Alltoall(&send_lengths[0], 1, MPI_INT, &recv_lengths[0], 1, MPI_INT,comm);

	// Scan to get recv_disps
	std::vector<int> recv_disps = exscan(recv_lengths);

	// Do all2allv to get data on correct processor
	El::Complex<double> * recv_data = Y.Buffer();
	//MPI_Alltoallv(&send_data[0],&send_lengths[0],&send_disps[0],MPI_DOUBLE, \
	//		&recv_data[0],&recv_lengths[0],&recv_disps[0],MPI_DOUBLE,comm);
	El::mpi::AllToAll(&send_data[0], &send_lengths[0], &send_disps[0], recv_data,&recv_lengths[0],&recv_disps[0],comm);

	if(print){
		std::cout << "Send data: " <<std::endl << send_data <<std::endl;
		std::cout << "Send lengths: " <<std::endl << send_lengths <<std::endl;
		std::cout << "Send disps: " <<std::endl << send_disps <<std::endl;
		std::cout << "Recv data: " <<std::endl << recv_data <<std::endl;
		std::cout << "Recv lengths: " <<std::endl << recv_lengths <<std::endl;
		std::cout << "Recv disps: " <<std::endl << recv_disps <<std::endl;
	}

	return 0;
}

int tree2elemental(InvMedTree<FMM_Mat_t> *tree, El::DistMatrix<T,El::VC,El::STAR> &Y){

	int data_dof=2;
	int SCAL_EXP = 1;

	int nlocal,gsize; //local elements, start p_id, global size
	double *pt_array; // will hold local array
	int r,q,rq; //Grid sizes
	int nbigs; //Number of large sends (i.e. send 1 extra data point)
	int pstart; // p_id of nstart
	int rank = El::mpi::WorldRank(); //p_id
	int send_size; // base send size
	bool print = rank == -1; 


	// Get Grid and associated params
	const El::Grid* g = &(Y.Grid());
	r = g->Height();
	q = g->Width();
	MPI_Comm comm = (g->Comm()).comm;

	std::vector<FMMNode_t*> nlist = tree->GetNGLNodes();

	int cheb_deg = InvMedTree<FMM_Mat_t>::cheb_deg;
	int omp_p=omp_get_max_threads();
	size_t n_coeff3=(cheb_deg+1)*(cheb_deg+2)*(cheb_deg+3)/6;

	// Get sizes, array in petsc 
	//VecGetSize(pt_vec,&gsize);
	gsize = tree->M/data_dof;
	nlocal = tree->m/data_dof;
	//VecGetLocalSize(pt_vec,&nlocal);
	//VecGetArray(pt_vec,&pt_array);
	int nstart = 0;
	MPI_Exscan(&nlocal,&nstart,1,MPI_INT,MPI_SUM,comm);
	//VecGetOwnershipRange(pt_vec,&nstart,NULL);

	//Find processor that nstart belongs to, number of larger sends
	rq = r * q;
	pstart = nstart % rq; //int div
	nbigs = nlocal % rq;
	send_size = nlocal/rq;
	
	if(print){
		std::cout << "r: " << r << " q: " << q <<std::endl;
		std::cout << "nstart: " << nstart << std::endl;
		std::cout << "ps: " << pstart << std::endl;
		std::cout << "nbigs: " << nbigs << std::endl;
		std::cout << "send_size: " << send_size << std::endl;
	}

	// Make send_lengths
	std::vector<int> send_lengths(rq);
	std::fill(send_lengths.begin(),send_lengths.end(),send_size);
	if(nbigs >0){
		for(int j=0;j<nbigs;j++){
			send_lengths[(pstart + j) % rq] += 1;
		}
	}

	// Make send_disps
	std::vector<int> send_disps = exscan(send_lengths);

	std::vector<El::Complex<double>> indata(nlocal);
	// copy the data from an ffm tree to into a local vec of complex data for sending #pragma omp parallel for
	for(size_t tid=0;tid<omp_p;tid++){
		size_t i_start=(nlist.size()* tid   )/omp_p;
		size_t i_end  =(nlist.size()*(tid+1))/omp_p;
		for(size_t i=i_start;i<i_end;i++){
			pvfmm::Vector<double>& coeff_vec=nlist[i]->ChebData();
			double s=std::pow(0.5,COORD_DIM*nlist[i]->Depth()*0.5*SCAL_EXP);

			size_t offset=i*n_coeff3;
			for(size_t j=0;j<n_coeff3;j++){
				double real = coeff_vec[j]*s; // local indices as in the pvfmm trees
				double imag = coeff_vec[j+n_coeff3]*s;
				El::Complex<double> coeff;
				El::SetRealPart(coeff,real);
				El::SetImagPart(coeff,imag);

				indata[offset+j] = coeff;
			}
		}
	}


	// Make send_data
	std::vector<El::Complex<double>> send_data(nlocal);
	for(int proc=0;proc<rq;proc++){
		int offset = send_disps[proc];
		int base_idx = (proc - pstart + rq) % rq; 
		for(int j=0; j<send_lengths[proc]; j++){
			int idx = base_idx + (j * rq);
			send_data[offset + j] = indata[idx];
		}
	}

	// Do all2all to get recv_lengths
	std::vector<int> recv_lengths(rq);
	MPI_Alltoall(&send_lengths[0], 1, MPI_INT, &recv_lengths[0], 1, MPI_INT,comm);
//.........这里部分代码省略.........

void El2Petsc_vec(El::DistMatrix<double,VC,STAR>& el_vec,Vec& pt_vec){
	PetscInt nlocal, nstart; // petsc vec info
	PetscScalar *pt_array,*pt_perm_array;
	int r,q,ll,rq; // el vec info
	int nbigs; //Number of large recv (i.e. recv 1 extra data point)
	int pstart; // p_id of nstart
	int p = El::mpi::WorldRank(); //p_id
	int recv_size; // base recv size
	bool print = p == -1; 

	// Get el vec info
	ll = el_vec.Height();
	const El::Grid* g = &(el_vec.Grid());
	r = g->Height();
	q = g->Width();
	MPI_Comm comm = (g->Comm()).comm;
	
	// Get petsc vec params
	VecGetLocalSize(pt_vec,&nlocal);
	VecGetArray(pt_vec,&pt_array);
	VecGetOwnershipRange(pt_vec,&nstart,NULL);

	// Determine who owns the first element we want
	rq = r * q;
	pstart = nstart % rq;
	nbigs = nlocal % rq;
	recv_size = nlocal / rq;
	
	if(print){
		std::cout << "r: " << r << " q: " << q <<std::endl;
		std::cout << "nstart: " << nstart << std::endl;
		std::cout << "ps: " << pstart << std::endl;
		std::cout << "nbigs: " << nbigs << std::endl;
		std::cout << "recv_size: " << recv_size << std::endl;
	}

	// Make recv sizes
	std::vector<int> recv_lengths(rq);
	std::fill(recv_lengths.begin(),recv_lengths.end(),recv_size);
	if(nbigs >0){
		for(int i=0;i<nbigs;i++){
			recv_lengths[(pstart + i) % rq] += 1;
		}
	}

	// Make recv disps
	std::vector<int> recv_disps = exscan(recv_lengths);

	// All2all to get send sizes
	std::vector<int> send_lengths(rq);
	MPI_Alltoall(&recv_lengths[0], 1, MPI_INT, &send_lengths[0], 1, MPI_INT,comm);

	// Scan to get send_disps
	std::vector<int> send_disps = exscan(send_lengths);

	// Do all2allv to get data on correct processor
	std::vector<double> recv_data(nlocal);
	MPI_Alltoallv(el_vec.Buffer(),&send_lengths[0],&send_disps[0],MPI_DOUBLE, \
			&recv_data[0],&recv_lengths[0],&recv_disps[0],MPI_DOUBLE,comm);
	
	if(print){
		//std::cout << "Send data: " <<std::endl << *el_vec.Buffer() <<std::endl;
		std::cout << "Send lengths: " <<std::endl << send_lengths <<std::endl;
		std::cout << "Send disps: " <<std::endl << send_disps <<std::endl;
		std::cout << "Recv data: " <<std::endl << recv_data <<std::endl;
		std::cout << "Recv lengths: " <<std::endl << recv_lengths <<std::endl;
		std::cout << "Recv disps: " <<std::endl << recv_disps <<std::endl;
	}
	
	// Reorder for petsc
	for(int p=0;p<rq;p++){
		int base_idx = (p - pstart + rq) % rq;
		int offset = recv_disps[p];
		for(int i=0;i<recv_lengths[p];i++){
			pt_array[base_idx + rq*i] = recv_data[offset + i];
		}
	}

	// Copy into array
	VecRestoreArray(pt_vec,&pt_array);
}

void Petsc2El_vec(Vec& pt_vec,El::DistMatrix<double,VC,STAR>& el_vec){
	PetscInt nlocal,nstart,gsize; //local elements, start p_id, global size
	PetscScalar *pt_array; // will hold local array
	int r,q,rq; //Grid sizes
	int nbigs; //Number of large sends (i.e. send 1 extra data point)
	int pstart; // p_id of nstart
	int p = El::mpi::WorldRank(); //p_id
	int send_size; // base send size
	bool print = p == -1; 


	// Get Grid and associated params
	const El::Grid* g = &(el_vec.Grid());
	r = g->Height();
	q = g->Width();
	MPI_Comm comm = (g->Comm()).comm;

	// Get sizes, array in petsc 
	VecGetSize(pt_vec,&gsize);
	VecGetLocalSize(pt_vec,&nlocal);
	VecGetArray(pt_vec,&pt_array);
	VecGetOwnershipRange(pt_vec,&nstart,NULL);

	//Find processor that nstart belongs to, number of larger sends
	rq = r * q;
	pstart = nstart % rq; //int div
	nbigs = nlocal % rq;
	send_size = nlocal/rq;
	
	if(print){
		std::cout << "r: " << r << " q: " << q <<std::endl;
		std::cout << "nstart: " << nstart << std::endl;
		std::cout << "ps: " << pstart << std::endl;
		std::cout << "nbigs: " << nbigs << std::endl;
		std::cout << "send_size: " << send_size << std::endl;
	}

	// Make send_lengths
	std::vector<int> send_lengths(rq);
	std::fill(send_lengths.begin(),send_lengths.end(),send_size);
	if(nbigs >0){
		for(int j=0;j<nbigs;j++){
			send_lengths[(pstart + j) % rq] += 1;
		}
	}

	// Make send_disps
	std::vector<int> send_disps = exscan(send_lengths);

	// Make send_data
	std::vector<double> send_data(nlocal);
	for(int proc=0;proc<rq;proc++){
		int offset = send_disps[proc];
		int base_idx = (proc - pstart + rq) % rq; 
		for(int j=0; j<send_lengths[proc]; j++){
			int idx = base_idx + (j * rq);
			send_data[offset + j] = pt_array[idx];
		}
	}

	// Do all2all to get recv_lengths
	std::vector<int> recv_lengths(rq);
	MPI_Alltoall(&send_lengths[0], 1, MPI_INT, &recv_lengths[0], 1, MPI_INT,comm);

	// Scan to get recv_disps
	std::vector<int> recv_disps = exscan(recv_lengths);

	// Do all2allv to get data on correct processor
	double * recv_data = el_vec.Buffer();
	MPI_Alltoallv(&send_data[0],&send_lengths[0],&send_disps[0],MPI_DOUBLE, \
			&recv_data[0],&recv_lengths[0],&recv_disps[0],MPI_DOUBLE,comm);

	if(print){
		std::cout << "Send data: " <<std::endl << send_data <<std::endl;
		std::cout << "Send lengths: " <<std::endl << send_lengths <<std::endl;
		std::cout << "Send disps: " <<std::endl << send_disps <<std::endl;
		std::cout << "Recv data: " <<std::endl << recv_data <<std::endl;
		std::cout << "Recv lengths: " <<std::endl << recv_lengths <<std::endl;
		std::cout << "Recv disps: " <<std::endl << recv_disps <<std::endl;
	}
}

 static type build_compatible(int m, int n, const El::DistMatrix<F, U, V>& A) {
     return type(m, n, A.Grid(), A.Root());
 }