Why is MATLAB R2019b very slow when clearing large variables from memory?

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I have a workstation with Intel i7 9900K and 64 GB (DDR4, 3200 MHz) of RAM. My recent project requires me to load 3-8 large structure arrays into the memory, occupying 10-40 GB of memory in total. I find that MATLAB (R2019b update 3) gets very slow when clearing these large variables from workspace. The "clear" command takes 30-60 seconds to finish, and from the Windows task manager I can see the memory usage gradually goes down. This happens even when aborting a function which loads the variables inside. The system has a pagefile of around 9 GB on an SSD but the memory usage (including all programs) never goes beyond 85% of total memory. I hope to know whether such slow clearing speed is a expected MATLAB behavior?
  4 Comments
Guillaume
Guillaume on 3 Feb 2020
That's 50000*20 arrays that all need to be freed individually. That's a lot of arrays!
Also, if you're not on 2019b update 4, see if installing the update improves performance.
Walter Roberson
Walter Roberson on 3 Feb 2020
Symbolic expressions stored in the symbolic engine can also be pretty slow to be removed, even when you quit MATLAB.

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