How can I start a 32bit MATLAB from a 64bit MATLAB and the other way around through COM in MATLAB R2014b?

I like to start a 32bit MATLAB from a 64bit MATLAB through COM and also to start a 32bit MATLAB from a 64bit MATLAB. The MATLABs are all the same version (R2014b). I registered both MATLAB version as COM servers. But when I simply use 

ml = actxserver('matlab.application')

then the 64bit MATLAB starts a 64bit MATLAB and the 32bit MATLAB starts a 32bit MATLAB.

Answer 1

[MathWorks Support Team]

This is expected behavior and related to the ay applications processing the registry on Windows. 

In order to be able to control the bittedness you would need to start the particular version of MATLAB through the command line with the /MLAutomation flag 

>>system('"C:\Program Files (x86)\MATLAB\R2014b\bin\win32\MATLAB.exe" /MLAutomation')

and then connect to it using 

>>ml = actxGetRunningServer('MATLAB.Application')

You can query the registry to find the installation folders of MATLAB automatically. Since 32bit application do not see the 64bit registry per default you would need to use:

https://www.mathworks.com/matlabcentral/answers/94683-why-am-i-unable-to-access-certain-registry-keys-from-r2014b-32-bit-on-a-64-bit-windows-operating-sys

An example would be (only works if 32bit AND 64bit MATLAB of the same version are registered)

CLSID = winqueryreg('HKEY_CLASSES_ROOT','MATLAB.Application\CLSID');
if strcmp(computer('arch'),'win64')
    %start 32bit MATLAB from a 64bit MATLAB
    ML_pth = winqueryreg('HKEY_CLASSES_ROOT',['Wow6432Node\CLSID\',CLSID,'\LocalServer32']);
else
    %start 64bit MATLAB from a 32bit MATLAB    
    ML_pth = winqueryreg64('HKEY_CLASSES_ROOT',['CLSID\',CLSID,'\LocalServer32']);
end

ML_pth = strrep(ML_pth,'.exe','.exe"');
system(sprintf('"%s &',ML_pth));
%since the above command is non blocking we have to wait a bit until MATLAB is fully started
pause(10);
ml = actxGetRunningServer('MATLAB.Application')