Can an object with a `Transient` property be used in a parfor loop?
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Naor Movshovitz on 19 Mar 2017
In a class I am using a private property A, an NxN matrix, to store data that is expensive to compute and may be used many times during the lifetime of the object. I was excited to learn about the Transient attribute which seems perfect for this type of property:
...a Transient property useful for cases where data needs to be stored
in the object temporarily as an intermediate computation step, or for
Easy and elegant solution but a method fails with a "array out of bounds" error when a parallel pool is available. I think the reason is clear enough: MATLAB calls save/load behind the scenes to send my object to workers in the parpool.
- Am I right about the cause and is this a documented limitation of the Transient attribute?
- Is there a workaround that doesn't require the property A to be recomputed by each worker?
Walter Roberson on 19 Mar 2017
Edited: Walter Roberson on 20 Mar 2017
The documentation https://www.mathworks.com/help/matlab/matlab_oop/property-attributes.html describes transient in terms of saving to file, but parfor effectively saves objects to file and reconstructs them on the worker. (it probably serializes into memory and transmits that by message passing, but the effect is the same.)
If you have only a small number of objects entering the parfor loop at any one time then possibly extract the property and transmit it to the workers as a parpool constant.