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goldsteinngoldsteinn
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pythongh-93033: Use wmemchr in stringlib (pythonGH-93034)
Generally comparable perf for the "good" case where memchr doesn't return any collisions (false matches on lower byte) but clearly faster with collisions.
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Lines changed: 39 additions & 14 deletions

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‎Misc/NEWS.d/next/Library/2022-05-22-23-46-18.gh-issue-93033.wZfiL-.rst‎

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@@ -0,0 +1 @@
1+
Search in some strings (platform dependent i.e [U+0xFFFF, U+0x0100] on Windows or [U+0xFFFFFFFF, U+0x00010000] on Linux 64-bit) are now up to 10 times faster.

‎Objects/bytearrayobject.c‎

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@@ -1096,6 +1096,7 @@ bytearray_dealloc(PyByteArrayObject *self)
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#define STRINGLIB_ISSPACE Py_ISSPACE
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#define STRINGLIB_ISLINEBREAK(x) ((x == '\n') || (x == '\r'))
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#define STRINGLIB_CHECK_EXACT PyByteArray_CheckExact
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#define STRINGLIB_FAST_MEMCHR memchr
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#define STRINGLIB_MUTABLE 1
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#include "stringlib/fastsearch.h"

‎Objects/bytes_methods.c‎

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@@ -431,6 +431,7 @@ _Py_bytes_maketrans(Py_buffer *frm, Py_buffer *to)
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#define STRINGLIB(F) stringlib_##F
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#define STRINGLIB_CHAR char
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#define STRINGLIB_SIZEOF_CHAR 1
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#define STRINGLIB_FAST_MEMCHR memchr
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#include "stringlib/fastsearch.h"
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#include "stringlib/count.h"

‎Objects/stringlib/asciilib.h‎

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@@ -21,6 +21,7 @@
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#define STRINGLIB_CHECK PyUnicode_Check
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#define STRINGLIB_CHECK_EXACT PyUnicode_CheckExact
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#define STRINGLIB_MUTABLE 0
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#define STRINGLIB_FAST_MEMCHR memchr
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#define STRINGLIB_TOSTR PyObject_Str
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#define STRINGLIB_TOASCII PyObject_ASCII

‎Objects/stringlib/fastsearch.h‎

Lines changed: 22 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -39,7 +39,7 @@
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#define STRINGLIB_BLOOM(mask, ch) \
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((mask & (1UL << ((ch) & (STRINGLIB_BLOOM_WIDTH -1)))))
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42-
#if STRINGLIB_SIZEOF_CHAR == 1
42+
#ifdef STRINGLIB_FAST_MEMCHR
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# define MEMCHR_CUT_OFF 15
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#else
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# define MEMCHR_CUT_OFF 40
@@ -53,8 +53,8 @@ STRINGLIB(find_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
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p = s;
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e = s + n;
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if (n > MEMCHR_CUT_OFF) {
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#if STRINGLIB_SIZEOF_CHAR == 1
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p = memchr(s, ch, n);
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#ifdef STRINGLIB_FAST_MEMCHR
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p = STRINGLIB_FAST_MEMCHR(s, ch, n);
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if (p != NULL)
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return (p - s);
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return -1;
@@ -102,16 +102,26 @@ STRINGLIB(find_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
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return -1;
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}
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105+
#undef MEMCHR_CUT_OFF
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107+
#if STRINGLIB_SIZEOF_CHAR == 1
108+
# define MEMRCHR_CUT_OFF 15
109+
#else
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# define MEMRCHR_CUT_OFF 40
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#endif
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Py_LOCAL_INLINE(Py_ssize_t)
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STRINGLIB(rfind_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
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{
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const STRINGLIB_CHAR *p;
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#ifdef HAVE_MEMRCHR
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/* memrchr() is a GNU extension, available since glibc 2.1.91.
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it doesn't seem as optimized as memchr(), but is still quite
112-
faster than our hand-written loop below */
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/* memrchr() is a GNU extension, available since glibc 2.1.91. it
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doesn't seem as optimized as memchr(), but is still quite
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faster than our hand-written loop below. There is no wmemrchr
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for 4-byte chars. */
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114-
if (n > MEMCHR_CUT_OFF) {
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if (n > MEMRCHR_CUT_OFF) {
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#if STRINGLIB_SIZEOF_CHAR == 1
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p = memrchr(s, ch, n);
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if (p != NULL)
@@ -139,19 +149,19 @@ STRINGLIB(rfind_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
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if (*p == ch)
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return n;
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/* False positive */
142-
if (n1 - n > MEMCHR_CUT_OFF)
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if (n1 - n > MEMRCHR_CUT_OFF)
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continue;
144-
if (n <= MEMCHR_CUT_OFF)
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if (n <= MEMRCHR_CUT_OFF)
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break;
146-
s1 = p - MEMCHR_CUT_OFF;
156+
s1 = p - MEMRCHR_CUT_OFF;
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while (p > s1) {
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p--;
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if (*p == ch)
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return (p - s);
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}
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n = p - s;
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}
154-
while (n > MEMCHR_CUT_OFF);
164+
while (n > MEMRCHR_CUT_OFF);
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}
156166
#endif
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}
@@ -165,7 +175,7 @@ STRINGLIB(rfind_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
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return -1;
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}
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168-
#undef MEMCHR_CUT_OFF
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#undef MEMRCHR_CUT_OFF
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170180
/* Change to a 1 to see logging comments walk through the algorithm. */
171181
#if 0 && STRINGLIB_SIZEOF_CHAR == 1

‎Objects/stringlib/replace.h‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -29,9 +29,9 @@ STRINGLIB(replace_1char_inplace)(STRINGLIB_CHAR* s, STRINGLIB_CHAR* end,
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if (!--attempts) {
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/* if u1 was not found for attempts iterations,
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use FASTSEARCH() or memchr() */
32-
#if STRINGLIB_SIZEOF_CHAR == 1
32+
#ifdef STRINGLIB_FAST_MEMCHR
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s++;
34-
s = memchr(s, u1, end - s);
34+
s = STRINGLIB_FAST_MEMCHR(s, u1, end - s);
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if (s == NULL)
3636
return;
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#else

‎Objects/stringlib/stringdefs.h‎

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@@ -24,4 +24,5 @@
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#define STRINGLIB_CHECK_EXACT PyBytes_CheckExact
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#define STRINGLIB_TOSTR PyObject_Str
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#define STRINGLIB_TOASCII PyObject_Repr
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#define STRINGLIB_FAST_MEMCHR memchr
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#endif /* !STRINGLIB_STRINGDEFS_H */

‎Objects/stringlib/ucs1lib.h‎

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@@ -20,6 +20,7 @@
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#define STRINGLIB_NEW _PyUnicode_FromUCS1
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#define STRINGLIB_CHECK PyUnicode_Check
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#define STRINGLIB_CHECK_EXACT PyUnicode_CheckExact
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#define STRINGLIB_FAST_MEMCHR memchr
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#define STRINGLIB_MUTABLE 0
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#define STRINGLIB_TOSTR PyObject_Str

‎Objects/stringlib/ucs2lib.h‎

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@@ -21,6 +21,10 @@
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#define STRINGLIB_CHECK PyUnicode_Check
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#define STRINGLIB_CHECK_EXACT PyUnicode_CheckExact
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#define STRINGLIB_MUTABLE 0
24+
#if SIZEOF_WCHAR_T == 2
25+
#define STRINGLIB_FAST_MEMCHR(s, c, n) \
26+
(Py_UCS2 *)wmemchr((const wchar_t *)(s), c, n)
27+
#endif
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2529
#define STRINGLIB_TOSTR PyObject_Str
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#define STRINGLIB_TOASCII PyObject_ASCII

‎Objects/stringlib/ucs4lib.h‎

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@@ -21,6 +21,10 @@
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#define STRINGLIB_CHECK PyUnicode_Check
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#define STRINGLIB_CHECK_EXACT PyUnicode_CheckExact
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#define STRINGLIB_MUTABLE 0
24+
#if SIZEOF_WCHAR_T == 4
25+
#define STRINGLIB_FAST_MEMCHR(s, c, n) \
26+
(Py_UCS4 *)wmemchr((const wchar_t *)(s), c, n)
27+
#endif
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2529
#define STRINGLIB_TOSTR PyObject_Str
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#define STRINGLIB_TOASCII PyObject_ASCII

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