On 02/01/2010 12:58 PM, Anders Wallin wrote:
How difficult is it to make boost-python play nice with OpenMP? Anyone
done it? Is this ever going to be a feature of boost-python, or always
going to require special patching and hacking?
I'm not sure in how much boost.python would actually need to care about
this. Presumably, some OpenMP support needs to be provided by the runtime
library (such as the thread management), so I would expect the Python binary
(or whatever your main application is) to be responsible for initializing
the right runtime library / support.
What compiler are you using ? Does it provide some documentation on what
needs to be done to activate OpenMP at runtime ?
I am using GCC 4.4.1
The pure C++ code with OpenMP compiles and runs fine using many
threads. There is almost a linear speedup of trivially parallel
for-loops.
When this same code is wrapped with boost-python and called from
Python that speedup disappears, i.e. the Python GIL(?, or something
similar), forces the C++ code to run in a single thread, or only one
thread to execute at a time.
I'm not convinced of this. It is true that there may only ever be one
thread accessing the Python runtime (thus the GIL to enforce it). But
you may certainly have as many threads doing other work as you want. And
if your OpenMP-enabled code is pure C++, with no hooks into the Python
runtime, then I don't see why that may not work.
Again: If your OpenMP-using code and the Python-exposed API are well
isolated, I don't think either needs to know about the other.
Stefan
--
...ich hab' noch einen Koffer in Berlin...
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