MATLAB: Do I receive an error using LOADLIBRARY when I use two workers in a single machine using Distributed Computing Toolbox 3.1 (R2007a)

Parallel Computing Toolbox

I am running a set of tasks on 8 workers. On workers that were sharing a machine, I observed the following errors sporadically:

 Error using ==> loadlibrary at 295
 The mfile describing your library could not be found possible Perl or file system error.
 and

 Error using ==> loadlibrary at 282
 Call to Perl failed.  Possible error processing header file.
 Output of Perl command:
 Can not open file PTDLL.i because No such file or directory at C:\Program Files\MATLAB\R2007a\MDCE\toolbox\matlab\general\private\prototypes.pl line 32.

Best Answer

In the call to LOADLIBRARY, a *.i file is generated when LCC is called to preprocess the header file of the dll. This file is placed in a temporary folder and may be deleted later. The issue is due to these temporary files being overwritten when two workers are run on the same machine.

To avoid this, you can use the MATLAB file prototype option while using LOADLIBRARY instead of the header. When LOADLIBRARY is used with MATLAB file prototyping option, MATLAB generates an file called a prototype file. This file can then be used on subsequent calls to LOADLIBRARY in place of a header file. The prototyping needs to be done only once and not at run-time and hence would avoid the temporary file conflict that could be causing the error.

Related Solutions

MATLAB: Do I receive a “LINK : error LNK2001: unresolved external symbol mexFunction” error when I attempt to mex a C++ source file using MATLAB 7.8 (R2009a)

The error received is a linker error which indicates that the C++ source file that is being MEXed does not contain the MEX gateway function "mexFunction".

To create a MEX file using source code that is present in multiple source files, provide all the source files as input to the MEX function. For example, if you have the following source files:

 fileContaininingMEXGateway.cpp
 sourceFile1.cpp
 sourcefile2.cpp

the MEX command to be used to create a a MEX file is shown below:

mex -v fileContaininingMEXGateway.cpp sourceFile1.cpp sourcefile2.cpp

MATLAB: Do I receive errors when trying to compile LOADLIBRARY or run an application that uses LOADLIBRARY with MATLAB Compiler 4.0 (R14)

This change has been incorporated into the documentation in Release 2011a (R2011a). For previous releases, read below for any additional information:

With MATLAB Compiler 4.0 (R14) and later, you can use MATLAB file prototypes as described below to load your library in a compiled application. Note that loading libraries using H-file headers is not supported in compiled applications.

This behavior occurs when LOADLIBRARY is compiled with the header argument as in the statement below:

loadlibrary(library, header)

In order to workaround this issue, execute the following command at the MATLAB commmand prompt:

loadlibrary(library, header, 'mfilename', 'mHeader');

... where mHeader is the name of a MATLAB file (in this case mHeader.m) that you would like to use when loading this library. This step only needs to be performed once to generate an MATLAB file for the library.

Now, in the code that is be compiled, you can call LOADLIBRARY with the following format:

loadlibrary(library, @mHeader, 'alias', alias)

With MATLAB Compiler versions 4.0.1 (R14+) and above, the generated MATLAB file mHeader.m will automatically be included in the CTF file as part of the compilation process. For versions 4.0 of the Compiler (R14) and later, include your library MATLAB file in the compilation with the '-a' option with MCC.

Note: With the MATLAB Compiler 3.0 (R13SP1) and earlier versions you cannot compile calls to LOADLIBRARY because of general restrictions and limitations of the MATLAB Compiler.

If you do not have a header file, the prototype file can be created manually. Follow the example in the documentation to generate a prototype file and modify it to suit the shared library you would like to use:

web([docroot,'/techdoc/ref/loadlibrary.html'])

Best Answer

Related Solutions

MATLAB: Do I receive a “LINK : error LNK2001: unresolved external symbol mexFunction” error when I attempt to mex a C++ source file using MATLAB 7.8 (R2009a)

MATLAB: Do I receive errors when trying to compile LOADLIBRARY or run an application that uses LOADLIBRARY with MATLAB Compiler 4.0 (R14)

Related Question