Why are memmap files saved twice during motion correction?

[programerkotik]

When running the parts of codes from the CNMF-E demo notebook for motion correction part, I observed that memmap files are saved twice:

1. First during the call to motion_correct(save_movie=True).
2. Again explicitly via cm.save_memmap.

Here:

%%time
if motion_correct:
    # do motion correction rigid
    mot_correct = MotionCorrect(movie_path, dview=cluster, **parameters.get_group('motion'))
    mot_correct.motion_correct(save_movie=True)
    fname_mc = mot_correct.fname_tot_els if pw_rigid else mot_correct.fname_tot_rig
    if pw_rigid:
        bord_px = np.ceil(np.maximum(np.max(np.abs(mot_correct.x_shifts_els)),
                                     np.max(np.abs(mot_correct.y_shifts_els)))).astype(int)
    else:
        bord_px = np.ceil(np.max(np.abs(mot_correct.shifts_rig))).astype(int)
        # Plot shifts
        plt.plot(mot_correct.shifts_rig)  # % plot rigid shifts
        plt.legend(['x shifts', 'y shifts'])
        plt.xlabel('frames')
        plt.ylabel('pixels')
        plt.gcf().set_size_inches(6,3)

    bord_px = 0 if border_nan == 'copy' else bord_px
    fname_new = cm.save_memmap(fname_mc, base_name='memmap_', order='C',
                               border_to_0=bord_px)
else:  # if no motion correction just memory map the file
    fname_new = cm.save_memmap(movie_path, base_name='memmap_',
                               order='C', border_to_0=0, dview=dview)

This redundancy becomes problematic with large datasets and it seems unnecessary to save the data twice, yet my attempts to bypass one of the saves lead to issues.

Question

Why are memmap files saved twice during motion correction?

The design seems intentional, but I wonder why. I noticed that one of them is saved in "F" order, and another one in "C". What is the meaning of that?

[kushalkolar]

Probably saving the memmap in C-order to run CNMF? There's no saving of memmaps twice for motion correction, mescore doesn't do it, the save_movie=True is how it's done.