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Optimize `scm_read_string'.

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According to the new benchmarks, this leads a 5% speed improvement when
reading small strings, and a 27% improvement when reading large strings.

* libguile/read.c (READER_STRING_BUFFER_SIZE): Change to 128; update
  comment to mention codepoints.
  (scm_read_string): Make `str' a list of strings, instead of a string.
  Store characters read in buffer `c_str'.  Cons to STR when C_STR is
  full, and concatenate/reverse at the end.

* benchmark-suite/benchmarks/read.bm (small, large): New variables.
  Set %DEFAULT-PORT-ENCODING to "UTF-8".
  ("read")["small strings", "large strings"]: New benchmarks.
This commit is contained in:
Ludovic Courtès 2012-05-07 00:32:01 +02:00
parent 5bbd632fc3
commit ff4d367275
2 changed files with 38 additions and 19 deletions
Download patch file Download diff file Expand all files Collapse all files

15
benchmark-suite/benchmarks/read.bm
View file

@ -1,6 +1,6 @@
;;; read.bm --- Exercise the reader. -*- Scheme -*-
;;;
;;; Copyright (C) 2008, 2010 Free Software Foundation, Inc.
;;; Copyright (C) 2008, 2010, 2012 Free Software Foundation, Inc.
;;;
;;; This program is free software; you can redistribute it and/or
;;; modify it under the terms of the GNU Lesser General Public License
@ -43,6 +43,11 @@
(load-file-with-reader file read buffering))
%files-to-load))
(define small "\"hello, world!\"")
(define large (string-append "\"" (make-string 1234 #\A) "\""))
(fluid-set! %default-port-encoding "UTF-8") ; for string ports
(with-benchmark-prefix "read"
@ -59,4 +64,10 @@
(exercise-read (list _IOFBF 8192)))
(benchmark "_IOFBF 16384" 10
(exercise-read (list _IOFBF 16384))))
(exercise-read (list _IOFBF 16384)))
(benchmark "small strings" 100000
(call-with-input-string small read))
(benchmark "large strings" 100000
(call-with-input-string large read)))

42
libguile/read.c
View file

@ -161,8 +161,8 @@ scm_i_read_hash_procedures_set_x (SCM value)
/* Size of the C buffer used to read symbols and numbers. */
#define READER_BUFFER_SIZE 128
/* Size of the C buffer used to read strings. */
#define READER_STRING_BUFFER_SIZE 512
/* Number of 32-bit codepoints in the buffer used to read strings. */
#define READER_STRING_BUFFER_SIZE 128
/* The maximum size of Scheme character names. */
#define READER_CHAR_NAME_MAX_SIZE 50
@ -493,15 +493,14 @@ scm_read_string (int chr, SCM port)
/* For strings smaller than C_STR, this function creates only one Scheme
object (the string returned). */
SCM str = SCM_BOOL_F;
unsigned c_str_len = 0;
scm_t_wchar c;
SCM str = SCM_EOL;
size_t c_str_len = 0;
scm_t_wchar c, c_str[READER_STRING_BUFFER_SIZE];
/* Need to capture line and column numbers here. */
long line = SCM_LINUM (port);
int column = SCM_COL (port) - 1;
str = scm_i_make_string (READER_STRING_BUFFER_SIZE, NULL, 0);
while ('"' != (c = scm_getc (port)))
{
if (c == EOF)
@ -511,12 +510,11 @@ scm_read_string (int chr, SCM port)
"end of file in string constant", SCM_EOL);
}
if (c_str_len + 1 >= scm_i_string_length (str))
{
SCM addy = scm_i_make_string (READER_STRING_BUFFER_SIZE, NULL, 0);
str = scm_string_append (scm_list_2 (str, addy));
}
if (c_str_len + 1 >= READER_STRING_BUFFER_SIZE)
{
str = scm_cons (scm_from_utf32_stringn (c_str, c_str_len), str);
c_str_len = 0;
}
if (c == '\\')
{
@ -580,12 +578,22 @@ scm_read_string (int chr, SCM port)
scm_list_1 (SCM_MAKE_CHAR (c)));
}
}
str = scm_i_string_start_writing (str);
scm_i_string_set_x (str, c_str_len++, c);
scm_i_string_stop_writing ();
c_str[c_str_len++] = c;
}
return maybe_annotate_source (scm_i_substring_copy (str, 0, c_str_len),
port, line, column);
if (scm_is_null (str))
/* Fast path: we got a string that fits in C_STR. */
str = scm_from_utf32_stringn (c_str, c_str_len);
else
{
if (c_str_len > 0)
str = scm_cons (scm_from_utf32_stringn (c_str, c_str_len), str);
str = scm_string_concatenate_reverse (str, SCM_UNDEFINED, SCM_UNDEFINED);
}
return maybe_annotate_source (str, port, line, column);
}
#undef FUNC_NAME