Mercurial > cpython-lru_cache-weakref
diff Modules/arraymodule.c @ 66688:48c40709417b
#1569291: speed up array.repeat() by making only O(log n) memcpy() calls; the code follows unicode_repeat.
| author | Georg Brandl <georg@python.org> |
|---|---|
| date | Sat, 04 Dec 2010 11:02:04 +0000 |
| parents | 62b61abd02b8 |
| children | 2581a17b29af |
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--- a/Modules/arraymodule.c Sat Dec 04 10:47:18 2010 +0000 +++ b/Modules/arraymodule.c Sat Dec 04 11:02:04 2010 +0000 @@ -674,11 +674,9 @@ static PyObject * array_repeat(arrayobject *a, Py_ssize_t n) { - Py_ssize_t i; Py_ssize_t size; arrayobject *np; - char *p; - Py_ssize_t nbytes; + Py_ssize_t oldbytes, newbytes; if (n < 0) n = 0; if ((Py_SIZE(a) != 0) && (n > PY_SSIZE_T_MAX / Py_SIZE(a))) { @@ -688,13 +686,23 @@ np = (arrayobject *) newarrayobject(&Arraytype, size, a->ob_descr); if (np == NULL) return NULL; - p = np->ob_item; - nbytes = Py_SIZE(a) * a->ob_descr->itemsize; - for (i = 0; i < n; i++) { - memcpy(p, a->ob_item, nbytes); - p += nbytes; + if (n == 0) + return (PyObject *)np; + oldbytes = Py_SIZE(a) * a->ob_descr->itemsize; + newbytes = oldbytes * n; + /* this follows the code in unicode_repeat */ + if (oldbytes == 1) { + memset(np->ob_item, a->ob_item[0], newbytes); + } else { + Py_ssize_t done = oldbytes; + Py_MEMCPY(np->ob_item, a->ob_item, oldbytes); + while (done < newbytes) { + Py_ssize_t ncopy = (done <= newbytes-done) ? done : newbytes-done; + Py_MEMCPY(np->ob_item+done, np->ob_item, ncopy); + done += ncopy; + } } - return (PyObject *) np; + return (PyObject *)np; } static int