c++ shared library startup options

Hi everyone. I have a question regarding compilation of c++ shared libraries and multithreading.

When creating a standalone executable i know that it is possible to specify startup option (i mostly use deploytool)

 -singleCompThread

to make sure that each MCR can only have one active computational thread.

As for C++ shared libraries i am not quite sure how this works. If i do not specify anything do the dll enable multiple threads?

and if so, how can i make sure that the shared library only uses one thread?

The project calling the c++ library is going to start several instances at once, and from testing with a standalone executable (and a .bat file) i have found out that the most effective way was to enable hyperthreading on my PC but only allow a single computational thread inside the matlab executable and run 8 instances at once ( i have 4 physical cores that turns into "8" when hyperthreaded ).

I have been searching the web for quite some time now and i cant find any examples that uses -singlecompthread for c++. The closest i got was the function

mclInitializeApplication

is this where -singleCompThread should be specified?

Any tips or clarifications would be highly appreciated as i am not very familiar with C++.

Thx in advance!

Answer 1

[Kaustubha Govind]

It looks like specifying the -singleCompThread option during compilation should also work.

For example:

>> mcc -R -singleCompThread -mv foo.m

[kjetil87]

mcc -W cpplib:test -R singleCompThread -T link:lib test

Error using mcc
Error: The option -R is invalid in library or component mode (specify -?
for help).

I guess i expected this since the MCR options tab wasnt there in deploytool for c++ library.

[Kaustubha Govind]

Ah! Sorry that didn't work. I'm not sure what else to recommend here. If you don't receive any other replies on this forum, you may want to contact MathWorks Tech Support.

[kjetil87]

Update: I have now created a C++ program to call my test library. It seems that

mclInitializeApplication

recognizes the command.

const char *opts[]={"-singleCompThread"}; 
mclInitializeApplication(opts, 1);

I tried giving a bogus character line instead of singleCompThread and then i got an error. I am still struggling to see the difference in core activity whether i specify this command or not but i guess it would have thrown an error if it didnt do anything.

Still im quite puzzled by all of this, because in the mathworks documentation of this function -singleCompThread is not listed as an option (but e.g -nojvm is, so thats why i assumed it should be given here). If anyone comes across any good information about this subject i would love to hear it ! :)