Info Catalog fftw3: Row-major Format fftw3: Multi-dimensional Array Format fftw3: Fixed-size Arrays in C

fftw3: Column-major Format

 
 3.2.2 Column-major Format
 -------------------------
 
 Readers from the Fortran world are used to arrays stored in
 "column-major" order (sometimes called "Fortran order").  This is
 essentially the exact opposite of row-major order in that, here, the
 _first_ dimension's index varies most quickly.
 
    If you have an array stored in column-major order and wish to
 transform it using FFTW, it is quite easy to do.  When creating the
 plan, simply pass the dimensions of the array to the planner in _reverse
 order_.  For example, if your array is a rank three 'N x M x L' matrix
 in column-major order, you should pass the dimensions of the array as if
 it were an 'L x M x N' matrix (which it is, from the perspective of
 FFTW). This is done for you _automatically_ by the FFTW legacy-Fortran
 interface (Calling FFTW from Legacy Fortran), but you must do it
 manually with the modern Fortran interface (Reversing array
 dimensions).
 

Info Catalog fftw3: Row-major Format fftw3: Multi-dimensional Array Format fftw3: Fixed-size Arrays in C