mirror of https://github.com/python/cpython
needforspeed: use "fastsearch" for count. this results in a 3x speedup
for the related stringbench tests.
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@ -5,6 +5,18 @@
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#include <ctype.h>
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#undef USE_INLINE /* XXX - set via configure? */
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#if defined(_MSC_VER) /* this is taken from _sre.c */
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#pragma warning(disable: 4710)
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/* fastest possible local call under MSVC */
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#define LOCAL(type) static __inline type __fastcall
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#elif defined(USE_INLINE)
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#define LOCAL(type) static inline type
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#else
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#define LOCAL(type) static type
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#endif
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#ifdef COUNT_ALLOCS
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int null_strings, one_strings;
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#endif
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@ -763,6 +775,108 @@ PyString_AsStringAndSize(register PyObject *obj,
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return 0;
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}
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/* -------------------------------------------------------------------- */
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/* Helpers */
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#define USE_FAST /* experimental fast search implementation */
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/* XXX - this code is copied from unicodeobject.c. we really should
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refactor the core implementations (see _sre.c for how this can be
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done), but that'll have to wait -- fredrik */
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/* fast search/count implementation, based on a mix between boyer-
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moore and horspool, with a few more bells and whistles on the top.
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for some more background, see: http://effbot.org/stringlib */
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/* note: fastsearch may access s[n], which isn't a problem when using
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Python's ordinary string types, but may cause problems if you're
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using this code in other contexts. also, the count mode returns -1
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if there cannot possible be a match in the target string, and 0 if
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it has actually checked for matches, but didn't find any. callers
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beware! */
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#define FAST_COUNT 0
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#define FAST_SEARCH 1
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LOCAL(Py_ssize_t)
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fastsearch(const unsigned char* s, Py_ssize_t n, const unsigned char* p,
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Py_ssize_t m, int mode)
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{
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long mask;
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int skip, count = 0;
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Py_ssize_t i, j, mlast, w;
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w = n - m;
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if (w < 0)
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return -1;
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/* look for special cases */
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if (m <= 1) {
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if (m <= 0)
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return -1;
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/* use special case for 1-character strings */
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if (mode == FAST_COUNT) {
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for (i = 0; i < n; i++)
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if (s[i] == p[0])
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count++;
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return count;
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} else {
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for (i = 0; i < n; i++)
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if (s[i] == p[0])
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return i;
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}
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return -1;
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}
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mlast = m - 1;
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/* create compressed boyer-moore delta 1 table */
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skip = mlast - 1;
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/* process pattern[:-1] */
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for (mask = i = 0; i < mlast; i++) {
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mask |= (1 << (p[i] & 0x1F));
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if (p[i] == p[mlast])
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skip = mlast - i - 1;
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}
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/* process pattern[-1] outside the loop */
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mask |= (1 << (p[mlast] & 0x1F));
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for (i = 0; i <= w; i++) {
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/* note: using mlast in the skip path slows things down on x86 */
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if (s[i+m-1] == p[m-1]) {
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/* candidate match */
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for (j = 0; j < mlast; j++)
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if (s[i+j] != p[j])
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break;
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if (j == mlast) {
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/* got a match! */
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if (mode != FAST_COUNT)
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return i;
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count++;
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i = i + mlast;
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continue;
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}
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/* miss: check if next character is part of pattern */
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if (!(mask & (1 << (s[i+m] & 0x1F))))
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i = i + m;
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else {
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i = i + skip;
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continue;
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}
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} else {
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/* skip: check if next character is part of pattern */
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if (!(mask & (1 << (s[i+m] & 0x1F))))
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i = i + m;
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}
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}
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if (mode != FAST_COUNT)
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return -1;
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return count;
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}
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/* -------------------------------------------------------------------- */
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/* Methods */
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static int
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@ -2177,7 +2291,7 @@ as in slice notation.");
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static PyObject *
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string_count(PyStringObject *self, PyObject *args)
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{
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const char *s = PyString_AS_STRING(self), *sub, *t;
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const char *s = PyString_AS_STRING(self), *sub;
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Py_ssize_t len = PyString_GET_SIZE(self), n;
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Py_ssize_t i = 0, last = PY_SSIZE_T_MAX;
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Py_ssize_t m, r;
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@ -2210,8 +2324,14 @@ string_count(PyStringObject *self, PyObject *args)
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if (n == 0)
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return PyInt_FromSsize_t(m-i);
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#ifdef USE_FAST
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r = fastsearch(s + i, last - i, sub, n, FAST_COUNT);
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if (r < 0)
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r = 0; /* no match */
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#else
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r = 0;
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while (i < m) {
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const char *t
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if (!memcmp(s+i, sub, n)) {
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r++;
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i += n;
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@ -2225,6 +2345,7 @@ string_count(PyStringObject *self, PyObject *args)
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break;
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i = t - s;
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}
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#endif
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return PyInt_FromSsize_t(r);
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}
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