# Memory usage of AverageTFR.plot()

**URL:** <https://mne.discourse.group/t/memory-usage-of-averagetfr-plot/3424>\
**Category:** Support & Discussions\
**Tags:** time-frequency, visualization\
**Created:** [July 19, 2021, 10:08am UTC](https://mne.discourse.group/t/memory-usage-of-averagetfr-plot/3424 "2021-07-19T10:08:21Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![cbrnr](https://yyz2.discourse-cdn.com/free1/user_avatar/mne.discourse.group/cbrnr/32/1409_2.png) [@cbrnr](https://mne.discourse.group/u/cbrnr)\
**Post date:** [July 19, 2021, 10:08am UTC](https://mne.discourse.group/t/memory-usage-of-averagetfr-plot/3424/1 "2021-07-19T10:08:21Z")

</div>

I’m computing and plotting several TFRs in a loop using `AverageTFR.plot()`. If I do not explicitly pass (a list of) `matplotlib.Axes` objects (i.e. the `axes` parameter gets its default value of `None`), the following `RuntimeWarning` is issued:

> More than 20 figures have been opened. Figures created through the pyplot interface (`matplotlib.pyplot.figure`) are retained until explicitly closed and may consume too much memory. (To control this warning, see the rcParam `figure.max_open_warning`).

Apparently, this warning is not generated by any MNE function, but I’m still asking this question here because it occurs when using `AverageTFR.plot()`. Indeed, I then tried to roll my own figure and axes objects (passing the latter to the `axes` parameter) and making sure to close the figure before plotting the next one. However, this doesn’t reduce memory usage at all, it doesn’t seem to make any difference.

Here’s a minimal example to demonstrate what I mean:

```python
import numpy as np
import mne
import matplotlib.pyplot as plt

n_channels = 64
n_freqs = 200
sfreq = 512
n_times = sfreq
nave = 60

rng = np.random.default_rng(seed=1)

for i in range(10):
    fig, axes = plt.subplots(1, n_channels)
    info = mne.create_info(n_channels, sfreq)
    data = rng.standard_normal((n_channels, n_freqs, n_times))
    times = np.arange(0, n_times / sfreq, 1 / sfreq)
    freqs = np.linspace(0, 50, n_freqs)
    tfr = mne.time_frequency.AverageTFR(info, data, times, freqs, nave)
    tfr.plot(picks="all", axes=axes, show=False)
    plt.close(fig)

```

I saved this script as `memtest.py` and ran it with the `mprof` function from the `memory-profiler` package:

```python
mprof run -T 0.05 memtest.py

```

The output obtained with `mprof plot` looks like this:

 ![Figure_1](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/f0c27f5f93aea155366c207f0d4226b3902ee1b8.png)

Apparently, closing the figure does not free any memory. For real data, this completely fills my 16GB of RAM and basically makes it impossible to loop over TFRs and plot them (actually I do not even want to plot, but I’m using `fig.save()` to export the figure to PNG).

Is this expected behavior or maybe a bug (if so, is it MNE or Matplotlib)? Maybe I’m not handling this correctly, so I’d appreciate any advice on how to efficiently plot multiple TFRs without swamping my RAM.

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<div class="post-metadata">

**Author:** ![richard](https://yyz2.discourse-cdn.com/free1/user_avatar/mne.discourse.group/richard/32/15_2.png) [@richard](https://mne.discourse.group/u/richard)\
**Post date:** [July 19, 2021, 1:47pm UTC](https://mne.discourse.group/t/memory-usage-of-averagetfr-plot/3424/2 "2021-07-19T13:47:54Z")

</div>

Can you try re-using the figure (that is, create it outside of the for loop)?

Have you tried calling the garbage collector manually after closing the figure?

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<div class="post-metadata">

**Author:** ![cbrnr](https://yyz2.discourse-cdn.com/free1/user_avatar/mne.discourse.group/cbrnr/32/1409_2.png) [@cbrnr](https://mne.discourse.group/u/cbrnr)\
**Post date:** [July 19, 2021, 2:00pm UTC](https://mne.discourse.group/t/memory-usage-of-averagetfr-plot/3424/3 "2021-07-19T14:00:08Z")

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> [@richard](#):
>
> Can you try re-using the figure (that is, create it outside of the for loop)?

Moving that line out of the loop reduces memory usage a little (it maxes out at around 1630MB as compared to 2240MB), but doesn’t change the fact that it is constantly growing.

> [@richard](#):
>
> Have you tried calling the garbage collector manually after closing the figure?

This doesn’t seem to change anything.