itpp.cpp

/*
 * Copyright (c) 2018-2020 Steven Varga, Toronto,ON Canada
 * Author: Varga, Steven <steven@vargaconsulting.ca>
 */
#include <iostream>
#include <itpp/itbase.h>
#include <h5cpp/all>
 
using namespace std;
// 
template<class T> using Matrix = itpp::Mat<T>;
template<class T> using Colvec = itpp::Vec<T>;
 
int main(){
    { // CREATE - WRITE
        Matrix<short> M(2,3);                                       // create a matrix
        h5::fd_t fd = h5::create("linalg.h5",H5F_ACC_TRUNC);    // and a file
        h5::ds_t ds = h5::create<short>(fd,"create then write"
                ,h5::current_dims{10,20}
                ,h5::max_dims{10,H5S_UNLIMITED}
                ,h5::chunk{2,3} | h5::fill_value<short>{3} |  h5::gzip{9}
        );
        h5::write( ds,  M, h5::offset{2,2}, h5::stride{1,3}  );
    }
 
    {
        Colvec<float> V(8);                               // create a vector
        // simple one shot write that computes current dimensions and saves matrix
        h5::write( "linalg.h5", "one shot create write",  V);
        // what if you want to position a matrix inside a higher dimension with some added complexity?  
        h5::write( "linalg.h5", "arma vec inside matrix",  V // object contains 'count' and rank being written
            ,h5::current_dims{40,50}  // control file_space directly where you want to place vector
            ,h5::offset{5,0}            // when no explicit current dimension given current dimension := offset .+ object_dim .* stride (hadamard product)  
            ,h5::count{1,1}, h5::stride{3,5}, h5::block{2,4}
            ,h5::max_dims{40,H5S_UNLIMITED}  // wouldn't it be nice to have unlimited dimension? if no explicit chunk is set, then the object dimension 
                             // is used as unit chunk
        );
    }
    { // CREATE - READ: we're reading back the dataset created in the very first step
      // note that data is only data, can be reshaped, cast to any format and content be modified through filtering 
        auto fd = h5::open("linalg.h5", H5F_ACC_RDWR,           // you can have multiple fd open with H5F_ACC_RDONLY, but single write
                h5::fclose_degree_strong | h5::sec2);          // and able to set various properties  
    }
    { // READ: 
        Matrix<short> M = h5::read<Matrix<short>>("linalg.h5","create then write"); // read entire dataset back with a single read
    }
}