[Numpy-discussion] Python ctypes and OpenMP mystery

Eric Carlson ecarlson at eng.ua.edu
Wed Feb 16 20:24:33 EST 2011

Hello Francesc,
The problem appears to related to my lack of optimization in the 
compilation. If I use

gcc -O3 -c my_lib.c -fPIC -fopenmp -ffast-math

the C executable and ctypes/python versions behave almost identically. 
Getting decent behavior takes some thought, though, far from the 
incredible almost-automatic behavior of numexpr.

Now I've got to figure out how to scale up a bunch of vector 
adds/multiplies. Neither numexpr or openmp get you very far with a bunch 
of "z=a*x+b*y"-type calcs.


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