C-extension 2 times slower than exe

Rolf Wester rolf.wester at ilt.fraunhofer.de
Tue Jun 23 10:20:44 EDT 2009

Philip Semanchuk wrote:
> On Jun 23, 2009, at 9:51 AM, Rolf Wester wrote:
>> Hi,
>> I have a C++ program that I would like to steer using Python. I made the
>> wrapper using swig and linked the code (without the main function) into
>> a shared object. My Python script loads the extension and calls a
>> function of the C-extension, the rest runs entirely within the
>> C-extension. For comparison I compiled the code including the main
>> function with the same compilation options and linked all into an exe.
>> The main function of the exe calls the same function as my Python script
>> does. Surprisingly the code in the Python C-extension runs twice as long
>> as the same code in the exe. Does anyone know what could be the reason
>> for this behaviour?
> If the runtime of the C/C++ code is short, the time spent initializing
> the Python interpreter might have a big impact on the runtime of the
> Python version.
The runtime is about 2.5 sec and 5.0 sec respectively. I not only use
the time command to measure the time consumed but I also measure the
time within the C-code using clock() and get similar result. So the
Python startup time is not the reason for the runtime difference I
found. Thank you anyway.


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