I've created a PR for adding an example which writes an Eigen::MatrixXd, see #531. It's supposed to create a matrix

  0    1    2
100  101  102
...
900  901  902

This matrix is then written to file. When dumping the resulting file I get

HDF5 "eigen_matrix_example.h5" {
GROUP "/" {
   DATASET "dset" {
      DATATYPE  H5T_IEEE_F64LE
      DATASPACE  SIMPLE { ( 10, 3 ) / ( 10, 3 ) }
      DATA {
      (0,0):   0,   100, 200,
      (1,0): 300, 400, 500,
      (2,0): 600, 700, 800,
      (3,0): 900,   1, 101,
      (4,0): 201, 301, 401,
      (5,0): 501, 601, 701,
      (6,0): 801, 901,   2,
      (7,0): 102, 202, 302,
      (8,0): 402, 502, 602,
      (9,0): 702, 802, 902
      }
   }
}
}

Which is consistent with HDF5 assuming data is row-major (C-style) and the actual Eigen matrix being column-major (Fortran/BLAS-style). I couldn't immediately find any code that transposes the matrix before writing it.

Note that a write-read cycle using HighFive returns, as expected, the same matrix.

Can someone confirm that I've set up the example properly and maybe comment on the desired behaviour?