Alexander Belopolsky <[email protected]> added the comment:
Mark> Does anyone feel like doing a speed comparison between Daniel's C patch
and a version with a direct no-frills iterative version of
factorial_part_product (i.e., just a simple 'for (i = n; i <= m; i += 2) {
<multiply running product by i> }?
Not a direct answer to your question, but replacing a bisect with a no-frills
algorithm in my precompute patch gives the following timings:
n bisect no-frills
100 38.9 us 38.5 us
1000 .904 ms 1.08 ms
10000 35.4 ms 50.3 ms
The no-frills product still takes 20 lines of C code though:
n = last - first + 1;
if (n <= 0)
return PyLong_FromLong(1L);
result = PyLong_FromUnsignedLong(ODD(first));
if (result == NULL)
return NULL;
for (i = 1; i < n; ++i) {
x = PyLong_FromUnsignedLong(ODD(first + i));
if (x == NULL)
goto error;
tmp = PyNumber_Multiply(result, x);
Py_DECREF(x);
if (tmp == NULL)
goto error;
Py_DECREF(result);
result = tmp;
}
return result;
error:
Py_DECREF(result);
return NULL;
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<http://bugs.python.org/issue8692>
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