Optimize Matplotlib Circuit Drawing: Auto-Close Figures to Prevent Memory Leak #13822
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### **Potential Memory Issue When Drawing a Circuit**
**Description**
When drawing quantum circuits using Matplotlib (`circ.draw(output='mpl')`), the figures are not automatically closed after being created. This leads to a memory leak and results in the following warning when creating many circuits:
```
RuntimeWarning: 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). Consider using matplotlib.pyplot.close().
mpl_figure = plt.figure()
```
**Steps to Reproduce**
1. Create and draw a quantum circuit in a loop:
```python
from qiskit import QuantumCircuit
for i in range(100):
circ = QuantumCircuit(2)
circ.h(0)
circ.cx(0, 1)
circ.draw(output='mpl')
```
2. Run the code via `python xxx.py`.
**Expected Behavior**
- Figures should be automatically closed after being drawn to avoid excessive memory usage.
- No warnings should be raised about too many open figures.
**Environment**
- Qiskit Version: 1.3.1
- Python Version: 3.10.15
- Running via `python xxx.py`
**Suggested Fix**
The issue arises because the figure object’s **lifetime** is not being properly managed. Matplotlib figures remain open in memory until explicitly closed, which leads to excessive memory consumption when many figures are drawn.
To solve this problem, we could either add a generator **autodeleter** to fix this problem
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It's very common to want to have more than one figure open at once. Even in your example for the functionality, it's necessary to have more than one figure open at once in order to even see the intermediate circuits drawn. Matplotlib gives you the tools to manage figures itself (e.g. |
Summary
Description
When drawing quantum circuits using Matplotlib (
circ.draw(output='mpl')), the figures are not automatically closed after being created. This leads to a memory leak and results in the following warning when creating many circuits:Steps to Reproduce
python xxx.py.Expected Behaviour
Details and comments
To solve this problem, we could either add a generator autodeleter to fix this problem