Re: [Help-glpk] Thread Safety of GLPK

[Heinrich Schuchardt]

Hello Simone,

in your program all threads create random file names that are generated
from the same name space. The initial value of the random number
generator probably will be the same for all threads. This will lead to
two threads trying to write the same file.

Either use a Singleton for the file name creation or use separate
namespaces by refering to the thread id like:
solution-<thread_id>-counter.txt

Your code lacks proper error handling for errors.

You should path unique filenames to the threads.

Please, have a look at glpk-4.63/examples/threads. It shows how to
handle GLPK errors in multithreaded applications.

The example code creates one thread per problem. In a real world program
you should use a thread pool.

Best regards

Heinrich Schuchardt


On 08/30/2017 05:51 AM, Simone Atzeni wrote:
> Hi all,
> 
> thanks for your answers.
> I updated to version 4.63, but I keep getting errors such as "segmentation 
> fault" or "glp_free: memory allocation error”.
> 
> I have a function, with a few parameters in input, which creates the MIP and 
> solve it (attached the function which creates the MIP).
> This function is called by multiple threads with different parameters and 
> they do not share any data.
> As soon as I call the function within a mutex lock/unlock everything works 
> fine.
> 
> I compiled the GLPK package with Clang/LLVM 4.9 which has support for TLS, so 
> I think everything should be fine.
> Do I need to do something else to make GLPK thread safe?
> 
> Thanks.
> Best,
> Simone