CODEWITHSUNDEEP
matlabscientific-computing
Nuno
Nuno

Reputation: 266

MATLAB: Does the execution of addpath/rmpath/savepath in one MATLAB instance affect other instances?

Does the execution of addpath/rmpath/savepath in one MATLAB instance affect other instances?

Motivation: Imagine that you are developing a MATLAB package, which provides a group of functions to the users. You have multiple versions of this package being developed on a single laptop. You would like to test these different versions in multiple instances of MATLAB:

See the pseudo-code below for a better idea about the tests.

No code or data is shared between different tests --- except for those embedded in MATLAB, as the tests are running on the same laptop, using the same installation of MATLAB. Below is a piece of pseudo-code for such a scenario.

% MATLAB instance 1

run_test(DIRECTORY_OF_PACKAGE_VERSION1);

% MATLAB instance 2

run_test(DIRECTORY_OF_PACKAGE_VERSION2);

% Code for the tests

function run_test(package_directory)

setup_package(package_dirctory);

RUN EXPERIMENTS TO TEST THE FUNCTIONS PROVIDED BY THE PACKAGE;

uninstall_package(package_directory);  

end

% This is the setup of the package that you are developing. 
% It should be called as a black box in the tests. 

function setup_package(package_dirctory)

addpath(PATH_TO_THE_FUNCTIONS_PROVIDED_BY_THE_PACKAGE);

% Make the package available in subsequent MATLAB sessions
savepath;  

end

% The function that uninstalls the package: remove the paths
% added by `setup_package` and delete the files etc.

function uninstall_package(package_directory)

rmpath(PATH_TO_THE_FUNCTIONS_PROVIDED_BY_THE_PACKAGE);

savepath; 

end

You want to make sure the following.

Hence here come our questions.

Questions:

  1. Does the execuation of addpath, rmpath, and savepath in one MATLAB instance affect the other instance, sooner or later?

  2. More generally, what kind of commands executed in one MATLAB instance can affect the other instance？

3. What if I am running only one instance of MATLAB, but invoke a parfor loop with two loops running in parallel? Does the execution of addpath/rmpath/savepath in one loop affect the other loop, sooner or later? In general, what kind of commands executed in one parallel loop can affect the other loop? (As pointed out by @Edric, this can be complicated; so let us not worry about it. Thank you, @Edric.)

Thank you very much for any comments and insights. It would be much appreciated if you could direct me to relevant sections in the official documentation of MATLAB --- I did some searching in the documentation, but have not found an answer to my question.

BTW, in case you find that the test described in the pseudo code is conducted in a wrong/bad manner, I will be very grateful if you could recommend a better way of doing it.

Upvotes: 0

Views: 282

Answers (1)

Edric
Edric

Reputation: 25160

The documentation page for the MATLAB Search Path specifies at the bottom:

When you change the search path, MATLAB uses it in the current session, but does not update pathdef.m. To use the modified search path in the current and future sessions, save the changes using savepath or the Save button in the Set Path dialog box. This updates pathdef.m.

So, standard MATLAB sessions are "isolated" in terms of their MATLAB Search Path unless you use savepath. After a call to savepath, new MATLAB sessions will read the updated pathdef.m on startup.

The situation with a parallel pool is slightly more complex. There are a couple of things that affect this. First is the parameter AutoAddClientPath that you can specify for the parpool command. When true, an attempt is made to reflect the desktop MATLAB's path on the workers. (This might not work if the workers cannot access the same folders).

When a parallel pool is running, any changes to the path on the desktop MATLAB client are sent to the workers, so they can attempt to add or remove path entries. Parallel pool workers calling addpath or rmpath do so in isolation. (I'm afraid I can't find a documentation reference for this).

Upvotes: 3

Related Questions