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2.2 KiB
2.2 KiB
Thread local memory example
===========================
The GLPK library, when compiled with default options, uses a separate environment
for each thread that is executed. So each thread is isolated. The only exeption
is error handling. An error in any of the library functions will not only
terminate the active thread but the complete process.
This can be circumvented by defining an error handling routine with
glp_error_hook(). This directory contains an example demonstrating running a
multithreaded application with error handling.
The example code
----------------
The program multiseed solves a MathProg model multiple times in separate parallel
threads. Each threads uses a different seed for the MathProg pseudo random number
generator.
The MathProg model clustering.mod generates 50 randomly distributed "towns". Out
of the towns it selects 3 to be cluster centers and assign the other towns to the
clusters such that the sum of the population weighted euclidian distances between
towns and centers is minimized.
The solution is written to a Scalable Vector File which can be viewed with a web
browser.
For demonstration purposes at the end of every third thread the error handling
routine is triggered by calling glp_error(). This results in output like
18-00086 Model has been successfully processed
18-00087 Voluntarily throwing an error in multiseed.c at line 147
18-00088 Error detected in file multiseed.c at line 146
18-00089 Error caught
Terminal output is preceeded by numbers indicating the thread index and the
output line. You can pipe it through sort to get a better overiew, e.g.
multiseed clustering.mod 20 | sort
Building and running the example code
-------------------------------------
On Linux multiseed can be compiled with gcc by calling
make
The code can be executed with
make check
For compiling the example on 64bit Windows with Microsoft Visual Studio C++ run
Build_Multiseed.bat
You may have to adust the variable HOME in the batch file depending on the
installation path of Visual Studio.
You can run multiseed with
multiseed <filename> <count>
Where filename is the path to the model file and count is the number of parallel
threads.