Optimizing Strings In Cython

I'm trying to demonstrate to our group the virtues of Cython for enhancing Python performance. I have shown several benchmarks, all that attain speed up by just: Compiling the ex

Solution 1:

I suggest you do your operations on cpython.array.arrays. The best documentation is the C API and the Cython source (see here).

from cpython cimport array

defcfuncA():
    cdefstr a
    cdefint i,j
    for j inrange(1000):
        a = ''.join([chr(i) for i inrange(127)])

defcfuncB():
    cdef:
        str a
        array.array[char] arr, template = array.array('c')
        int i, j

    for j inrange(1000):
        arr = array.clone(template, 127, False)

        for i inrange(127):
            arr[i] = i

        a = arr.tostring()

Note that the operations required vary very much on what you do to your strings.

>>>python2 -m timeit -s "import pyximport; pyximport.install(); import cyytn""cyytn.cfuncA()"
100 loops, best of 3: 14.3 msec per loop

>>>python2 -m timeit -s "import pyximport; pyximport.install(); import cyytn""cyytn.cfuncB()"
1000 loops, best of 3: 512 usec per loop

So that's a 30x speed-up in this case.

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Also, FWIW, you can take off another fair few µs by replacing arr.tostring() with arr.data.as_chars[:len(arr)] and typing a as bytes.