[Edu-sig] Introducing Python to Engineering Students

[David MacQuigg]

At 07:24 PM 3/11/2008 -0700, Rob Malouf wrote:

>On Mar 11, 2008, at 5:11 PM, David MacQuigg wrote:
>>It would make a nice improvement in this Mandelbrot demo if you  
>>could show me a way to significantly improve the speed of the Python  
>>I already have, perhaps avoiding the need for C.
>...
>Or, instead, replacing your getpts with the weave-d version:
>
>                from numpy import zeros
>                from scipy import weave
>                ...
>    vals = zeros(100,int)
>
>    code = r"""
>        double cx = cx0 - dx;
>        for (int p=0; p<100; p++) {
>            double zx = 0.0;
>            double zy = 0.0;
>            int i;
>            cx += dx;
>            for (i=0; i<999; i++) {
>                double zx2 = zx*zx;
>                double zy2 = zy*zy;
>                if ((zx2 + zy2) > 4.0) break;
>                zy = 2*zx*zy + cy0;
>                zx = zx2 - zy2 + cx;
>            }
>            vals[p] = i;
>        }
>    """
>    weave.inline(code,['cx0','cy0','dx','vals'])
>
>I get:
>
>    1a) Python speed = 102200 points/sec
>    1b) C speed      = 103300 points/sec
>    2a) Python speed = 108400 points/sec
>    2b) C      speed = 110700 points/sec

Excellent!!!  This is exactly what we need.  Our students will have no problem writing the C code string, and the Python wrappings are simple enough they can just follow this example verbatim.

>There's probably a more pythonic way to write that, but  
>this'll do.  And after all, this is a realistic situation: you've got  
>the inner loop of a program written in C, but you'd rather write all  
>the supporting code around it in something like Python.  And note that  
>weave automatically compiles and links (if necessary) and then loads  
>the C part when you run mandel.py.  You (or your students) don't need  
>to remember where the python headers are or how to build a shared  
>library on whatever platform they're using.

That was my next problem.  Our students use mostly Windows, some on MacOS, and a few on Linux.  If all we need beyond the latest Python is numpy and scipy, that is great!!

I'll have to experiment with this later.  Many thanks.

-- Dave