Export to C code

edit

Just to chime in here on this long abandoned question, the code generation module that DSM mentions is now included in Sage. Here's a short example:

sage: x, y = var('x, y')
sage: f = x**2 + sin(y)/sqrt(5*x+9*y)
sage: fs = f._sympy_() # convert to a sympy symbolic expression
sage: [(c_name, c_code), (h_name, c_header)] = codegen(("f", fs), "C", "test")
sage: print c_code
/******************************************************************************
 *                      Code generated with sympy 0.7.1                       *
 *                                                                            *
 *              See http://www.sympy.org/ for more information.               *
 *                                                                            *
 *                       This file is part of 'project'                       *
 ******************************************************************************/
#include "test.h"
#include <math.h>

double f(double x, double y) {

   return pow(x, 2) + sin(y)/sqrt(5*x + 9*y);

}

If I understand you, then you're looking for the equivalent of maple's CodeGeneration package, which nicely turns Maple functions into fortran or C code which you can then include in your own code (done this many times myself). Unfortunately I couldn't find what you're looking for.

(1) I tried looking at the existing expression conversions (for sympy, maxima, etc.) but none of them seemed to need to do this.

(2) Apparently there are tricks to do it from maxima (using the "subst" command), but I couldn't get any of them to work, at least not via the Sage-Maxima interface. My Maxima-fu is pretty weak, though. Unfortunately Fortran has the "**" operator, so using maxima.fortran wouldn't help!

(3) I don't think Cython will be that useful here, because the C code that it generates is pretty messy, and parsing it to recover something that you could insert in a non-Cython C code -- though doable -- would be much harder and more error-prone than simply turning (a)^(b) into pow((a), (b)) in the first place!

This would be a very useful feature, though; doing algebra in a CAS and then moving it to code used to be one of the main things I used Maple for.

Cython (included with Sage) converts Python-like code into C which can then be compiled into a shared-object library and used by Python / Sage. It's intended use is to write code that is easy to use like Python but is optimized to use fast C data types instead of slower Python data structures. However, one could certainly just write Python without any optimizations and have Cython generate the C equivalent.

Create a .pyx file containing your code and execute

$ sage -cython -a mycythonfile.pyx

This will output a corresponding .c file which can be compiled into a shared object library and imported in Python along with an.html file that neatly shows the C equivalent of each line of code.

Be warned that the corresponding C code, though optimized, looks really messy.

For more information on compiling Cython code, take a look at the Cython compilation documentation.

It looks like sympy 0.6.7 has a codegen package, but the version in Sage (0.6.4 in Sage 4.7) doesn't. We should upgrade and make sure it works with ._sympy_(), this is a very useful feature.

If you just add %cython to the beginning of the notebook it gives a c file. The file is a bit messy but you can always include it in other c files and call functions.

Hi Hennes,

Did you ever figure out how to translate Sage code into C code? I have the exact same problem and can't find a way to do that. Besides, the link cswiercz gave is now broken.

Just to add to the list of answers, I'm linking a post I've made which shows how to expand Benjamin Jones' solution to a system of functions and their gradients: http://louisgagnon.com/scBlog/sageCpp...