Metalone, 11.03.2010 23:57:
I just tried the seek test with Cython.
Cython fseek() : 1.059 seconds. 30% slower than 'C'
Python f.seek : 1.458 secondds. 80% slower than 'C'.
It is amazing to me that Cython generates a 'C' file that is 1478
lines.
Well, it generated an optimised Python interface for your module and made
it compilable in CPython 2.3 through 3.2. It doesn't look like your C
module features that. ;)
#Cython code
import time
cdef int SEEK_SET = 0
cdef extern from "stdio.h":
void* fopen(char* filename, char* mode)
int fseek(void*, long, int)
Cython ships with a stdio.pxd that you can cimport. It looks like it
doesn't currently define fseek(), but it defines at least fopen() and FILE.
Patches are always welcome.
def main():
cdef void* f1 = fopen('video.txt', 'rb')
cdef int i=1000000
t0 = time.clock()
while i> 0:
fseek(f1, 0, SEEK_SET)
i -= 1
delta = time.clock() - t0
Note that the call to time.clock() takes some time, too, so it's not
surprising that this is slower than hand-written C code. Did you test how
it scales?
Also, did you look at the generated C code or the annotated Cython code
(cython -a)? Did you make sure both were compiled with the same CFLAGS?
Also, any reason you're not using a for-in-xrange loop? It shouldn't make a
difference in speed, it's just more common. You even used a for loop in
your C code.
Finally, I'm not sure why you think that these 30% matter at all. In your
original post, you even state that seek-time isn't the "deal breaker", so
maybe you should concentrate on the real issues?
Stefan
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