[Paraview] Reading C-ordered data from hdf5

[John R. Cary]

Dominik Szczerba wrote:
> You will need SetArray method from the concrete implementation of 
> vtkDataArray. I could not quickly find in the source code any hints 
> about the underlying storage ordering, but it is trivial to find out 
> experimentally. Just post the results please. If it is the same as 
> yours no copying is needed.
>

Well, I was unable to figure out how to get hdf5 to read the data
in by Fortran order, so I wrote the snippet below.  Sending by
request.

This is probably slow, so better solutions always welcome.

John Cary

// The index tuple is initially zero
    size_t* indices = new size_t[rank];
    for(size_t k=0; k<rank; ++k) indices[k] = 0;
// Step through by global C index
    for(size_t k = 0; k<len; ++k) {
// Accumulate the Fortran index
      size_t indx = indices[rank-1];
      for(size_t j = 2; j<=rank; ++j) indx = indx*dims[rank-j] +
        indices[rank-j];
// Set the value in the VTK array at the Fortran index to the
// value in the C array at the C index
      if (H5Tequal(type, H5T_NATIVE_DOUBLE)) rv->SetTuple(indx,
        &((double*) data)[k]);
      if (H5Tequal(type, H5T_NATIVE_FLOAT)) rv->SetTuple(indx,
        &((float*) data)[k]);
// Update the index tuple
      size_t j = rank;
      do {
        --j;
        ++indices[j];
        if (indices[j] == dims[j]) indices[j] = 0;
        else break;
      } while (j != 0);
    }



>>>
>>> John R. Cary wrote:
>>>> I have arrays written out from C into HDF5 using the HDF5 C
>>>> API, and so in the file the arrays are in C ordering.  I now
>>>> need to read them into VTK.  AFAICT, VTK is Fortran ordering,
>>>> even though it is written in C++.  So that means I need to
>>>> reverse the ordering.  Of course, I can write a loop to do
>>>> this, but is there some standard way that VTK folks do this?
>>>> I don't want to reinvent the wheel.
>>>>
>>>> Sorry for what is likely an elementary question, but I could
>>>> not find it on the FAQ or after googling quite a bit.
>>>>
>>>> Thanks so much......John Cary
>>>>
>>>>
>>>
>>
>