从Python调用C Math函数的高效解决方案

Question

I have heard about different ways to call C functions from Python code, such as ctypes, cython, swig, Boost.python, etc. Each has pros and cons, of course. My question is about efficiency. I need to call C numerical functions from Python. A typical example of such a C function is:

double f(double x){
  return sin(x)+cos(x)-pow(2,x) + x*x;
}

The invocation needs to be iterated 2000-200000 times in one run.

Under such context, which C->Python transformer should I use?

Answer 1

Calling a function implemented in C will not magically make your program run faster. Not executing code written in Python might speed your program up. So you won't gain anything significant by moving such a simple function into a C routine. If you call it in a tight loop, the function itself might be fast but the overhead of the loop written in Python will completely dominate. So the general idea is to move tasks as large as possible into a C routine. In your example, this might be the entire loop. Once the chunk of work you do with a single call to a C function is large enough, the function call overhead itself will become negligible so you shouldn't worry about it that much. Call the function however you find it most convenient. Chances are high that it doesn't affect performance in a measurable way.