setLowerTriangularMatrix

C++ Function Reference

1 Signature

void BigDataStatMeth::setLowerTriangularMatrix(BigDataStatMeth::hdf5Dataset *dsMat, hsize_t dElementsBlock)

2 Description

Set the lower triangular matrix using block-based approach.

3 Parameters

• dsMat (BigDataStatMeth::hdf5Dataset *): The dataset to set the lower triangular matrix of
• dElementsBlock (hsize_t): The block size to use for the matrix

4 Details

Reads blocks, modifies them in memory to create lower triangular structure, and writes complete modified blocks instead of individual elements

5 Call Graph

6 Source Code

NoteImplementation

File: inst/include/hdf5Algebra/matrixTriangular.hpp • Lines 145-228

inline void setLowerTriangularMatrix( BigDataStatMeth::hdf5Dataset* dsMat, hsize_t dElementsBlock)
    {
        
        try {
            
            std::vector<hsize_t> stride = {1, 1},
                block = {1, 1};
            
            hsize_t readedRows = 0,
                rowstoRead,
                minimumBlockSize;
            
            // Optimized block size calculation
            minimumBlockSize = std::max(static_cast<hsize_t>(1024), 
                                        std::min(dElementsBlock, dsMat->nrows()));
            
            while ( readedRows < dsMat->nrows() ) {
                
                rowstoRead = ( -2 * readedRows - 1 + std::sqrt( pow(2*readedRows, 2) - 4 * readedRows + 8 * minimumBlockSize + 1) ) / 2;
                
                if( readedRows + rowstoRead > dsMat->nrows()) {
                    rowstoRead = dsMat->nrows() - readedRows;
                }
                
                // Read square block from diagonal position
                std::vector<hsize_t> offset = {readedRows, readedRows};
                std::vector<hsize_t> count = {rowstoRead, rowstoRead};
                
                // Read the current square block
                std::vector<double> block_data(rowstoRead * rowstoRead);
                dsMat->readDatasetBlock(offset, count, stride, block, block_data.data());
                
                // Map to Eigen matrix for easier manipulation
                Eigen::Map<Eigen::Matrix<double, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>> 
                    block_matrix(block_data.data(), rowstoRead, rowstoRead);
                
                // Create lower triangular: copy upper triangle to lower triangle
                for (hsize_t i = 0; i < rowstoRead; i++) {
                    for (hsize_t j = i + 1; j < rowstoRead; j++) {
                        block_matrix(j, i) = block_matrix(i, j);  // Copy upper to lower
                    }
                }
                
                // Write the complete modified block back - SINGLE WRITE OPERATION
                dsMat->writeDatasetBlock(Rcpp::wrap(block_matrix), offset, count, stride, block, false);
                
                // Handle rectangular regions outside the diagonal blocks
                if (readedRows + rowstoRead < dsMat->nrows()) {
                    // Write upper-right rectangular region (above diagonal block)
                    hsize_t remaining_cols = dsMat->nrows() - readedRows - rowstoRead;
                    std::vector<hsize_t> rect_offset = {readedRows, readedRows + rowstoRead};
                    std::vector<hsize_t> rect_count = {rowstoRead, remaining_cols};
                    
                    // Read upper-right block (source for transpose)
                    std::vector<double> rect_data(rowstoRead * remaining_cols);
                    dsMat->readDatasetBlock(rect_offset, rect_count, stride, block, rect_data.data());
                    
                    Eigen::Map<Eigen::Matrix<double, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>> 
                        rect_matrix(rect_data.data(), rowstoRead, remaining_cols);
                    
                    // Write transposed data to lower-left position
                    std::vector<hsize_t> lower_offset = {readedRows + rowstoRead, readedRows};
                    std::vector<hsize_t> lower_count = {remaining_cols, rowstoRead};
                    
                    Eigen::MatrixXd transposed = rect_matrix.transpose();
                    dsMat->writeDatasetBlock(Rcpp::wrap(transposed), lower_offset, lower_count, stride, block, false);
                }
                
                readedRows = readedRows + rowstoRead; 
            }
        }
        catch( H5::FileIException& error ) {
            Rcpp::Rcout<<"c++ exception setLowerTriangularMatrix (File IException)";
            return void();
        } catch( H5::DataSetIException& error ) {
            Rcpp::Rcout << "c++ exception setLowerTriangularMatrix (DataSet IException)";
            return void();
        } catch(std::exception& ex) {
            Rcpp::Rcout << "c++ exception setLowerTriangularMatrix: " << ex.what();
            return void();
        }
        
        return void();
    }

7 Usage Example

#include "BigDataStatMeth.hpp"

// Example usage
auto result = setLowerTriangularMatrix(...);