Slow Matlab startup if startup.m contains many path additions

I am asking/answering my own question, hoping it will help someone with the same issue:

If Matlab takes 3+ minutes to start up, how can I speed it up? My startup.m file contains many calls to add directories to my path, and those directories reside on a network drive. For example:

path(path, 'S:\top_code_directory\some_subdirectory') ; % Many calls like this
path(path, genpath('S:\project_directories')) ; % Many subdirectories are added

[Jan]

Please add an example for "add directories to my path". This will increase the chance, that others with the same problem will find this thread. Is the time wasted in addpath or in genpath? Thanks.

Answer 1

[Richard Crozier]

build the path yourself and do a single call to addpath, addpath expects a single string containing path names separated by semicolons. So try something like the following:

apath = 'S:\top_code_directory\some_subdirectory;'

newpath = [genpath('S:\project_directories'), apath];

addpath(newpath);

Obviously your construction of the path string to add will be more complex. Just remember that genpath already produces a string ending in a semicolon so you don't need to add one to the string produced by it.

You will find this much faster, as the bottleneck is the function path.m

[K E]

What is nice about this solution is that I can put this in my startup file. I've had the saved path (via my original savepath approach) get corrupted a couple times so having it in my startup will be more robust. Thanks for answering after all this time - shows the value of Answers in retaining / gaining knowledge.

Answer 2

[K E]

Most of the 3 minutes were spent generating Matlab's path, but it is not necessary to generate the path at each startup. Instead, remove the path calls from startup.m, save it, and restart Matlab, noting a faster startup. Generate the desired path from the command prompt using the same calls that used to be in the startup.m file, then execute the savepath command. Every subsequent time Matlab starts, it loads the saved path. The improvement in startup time can be verified using the -timing option as described here. Thanks to Tech Support for showing me this solution.

[Richard Crozier]

Well, this is ok, as long as the path directory structure never changes, and you have write permission to the directory where the path is saved, which in my case I don't, and don't want your startup script to be portable between different machines. Why not just do it throught the Set Path dialog in this case and choose save?

The real problem here is that calls to path.m are very slow.

[Robert Cumming]

By doing it this way every user of your machine will also have all your paths added. Be careful as you may not want this...

[Richard Crozier]

No, only users who have access to my startup directory which is only accessible to me, so they have to also be logged in as me. Valid point for others though. I've discovered the real answer to the problem anyway which I have posted below.