Use less memory when loading EDF file (#10638)

* Use less memory when loading EDF file * Add changelog entry * Formatting Co-authored-by: Alexandre Gramfort <alexandre.gramfort@m4x.org> * Restart CI Co-authored-by: Alexandre Gramfort <alexandre.gramfort@m4x.org>
mne-tools · May 17, 2022 · 9d972e4 · 9d972e4
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diff --git a/doc/changes/latest.inc b/doc/changes/latest.inc
@@ -100,6 +100,8 @@ Bugs
 
 - Fix bug in :func:`mne.viz.plot_evoked_image` that would cause incorrect sub-titles when using ``group_by`` (:gh:`10618` by `Reza Shoorangiz`_)
 
+- Reduce memory usage when loading an EDF file with ``preload=False`` (:gh:`10638` by `Clemens Brunner`_)
+
 API and behavior changes
 ~~~~~~~~~~~~~~~~~~~~~~~~
 - When creating BEM surfaces via :func:`mne.bem.make_watershed_bem` and :func:`mne.bem.make_flash_bem`, the ``copy`` parameter now defaults to ``True``. This means that instead of creating symbolic links inside the FreeSurfer subject's ``bem`` folder, we now create "actual" files. This should avoid troubles when sharing files across different operating systems and file systems (:gh:`10531` by `Richard Höchenberger`_)

diff --git a/mne/io/edf/edf.py b/mne/io/edf/edf.py
@@ -300,7 +300,8 @@ def _read_segment_file(data, idx, fi, start, stop, raw_extras, filenames,
             one = np.zeros((len(orig_sel), d_eidx - d_sidx), dtype=data.dtype)
             for ii, ci in enumerate(read_sel):
                 # This now has size (n_chunks_read, n_samp[ci])
-                ch_data = many_chunk[:, ch_offsets[ci]:ch_offsets[ci + 1]]
+                ch_data = many_chunk[:,
+                                     ch_offsets[ci]:ch_offsets[ci + 1]].copy()
 
                 if ci in tal_idx:
                     tal_data.append(ch_data)