pyvista: Memory Leak Using Plotter and Screenshot

Memory Leak Using Plotter and Screenshot

It seems that Plotter.screenshot() produces a memory leak. I am currently running an iterative program implementing the observer pattern, where after each iteration (i.e. when the observer is notified), the observer plots and saves (as a .png) OpenFOAM data.

What I notice in my Activity Monitor is that after each time the observer is called and executed (i.e. PlotVTK.update() is run), my python memory increases by around ~70MB, which becomes a problem when the observer is called around 300 times, when memory consumption has increased to many many GBs.

I have noticed that when I comment out p.screenshot(f'plot_{iteration}', window_size=[1000,1000], return_img = False) , my memory increase after each observer call is much smaller, i.e. 5MB. Although, when I don’t call this observer at all, my memory increase after each observer call in <1MB.

Any help would be appreciated.

My code

import Observer
import pyvista as pv

class PlotVTK(Observer):
    
    def update(self, subject) -> None:
        
        # Get current iteration
        iteration = subject.iteration
        
        # Open openfoam file
        reader = pv.OpenFOAMReader(f'test_{iteration}.foam')

        # Obtain data for latest snapshot
        reader.set_active_time_value(reader.time_values[-1])

        # Read data into mesh
        mesh = reader.read()

        # Extract internal mesh data
        internalMesh = mesh["internalMesh"].slice_orthogonal()

        # Create plotting environment
        p = pv.Plotter(off_screen = True)

        # Plot velocity diagram
        p.add_mesh(internalMesh, scalars = 'U')

        # Set viewing angle
        p.view_xy()
        p.camera_position = ((0, 0, 3), (0, 0, 0), (0, 0, 0))
        
        # Take screenshot of image and save in appropriate directory
        p.screenshot(f'plot_{iteration}', window_size=[1000,1000], return_img = False)

        # Clear plot data (i.e. release memory)
        p.clear()

---

System Information:

--------------------------------------------------------------------------------
  Date: Mon Feb 21 16:38:57 2022 GMT

                OS : Darwin
            CPU(s) : 8
           Machine : x86_64
      Architecture : 64bit
               RAM : 16.0 GiB
       Environment : IPython
       File system : apfs
        GPU Vendor : Apple
      GPU Renderer : Apple M1
       GPU Version : 4.1 Metal - 76.3

  Python 3.9.7 (default, Sep 16 2021, 08:50:36)  [Clang 10.0.0 ]

           pyvista : 0.33.2
               vtk : 9.1.0
             numpy : 1.21.2
           imageio : 2.16.0
           appdirs : 1.4.4
            scooby : 0.5.11
        matplotlib : 3.5.0
           IPython : 7.29.0
        ipyvtklink : 0.2.2
             scipy : 1.7.3
              tqdm : 4.62.3
--------------------------------------------------------------------------------