这是一个后续问题,有点像这个问题:写一个有效的字符串替换函数?.
在(尽管遥远的)未来,我希望能够进行自然语言处理。因此,字符串操作的速度当然很重要。偶然地,我偶然发现了这个测试:http ://raid6.com.au/~onlyjob/posts/arena/ - 所有测试都有偏见,这也不例外。然而,它对我提出了重要的问题。所以我写了一些测试来看看我做得怎么样:
这是我的第一次尝试(我称之为#A):
#一个
(defun test ()
(declare (optimize (debug 0) (safety 0) (speed 3)))
(loop with addidtion = (concatenate 'string "abcdefgh" "efghefgh")
and initial = (get-internal-real-time)
for i from 0 below (+ (* (/ 1024 (length addidtion)) 1024 4) 1000)
for ln = (* (length addidtion) i)
for accumulated = addidtion
then (loop with concatenated = (concatenate 'string accumulated addidtion)
for start = (search "efgh" concatenated)
while start do (replace concatenated "____" :start1 start)
finally (return concatenated))
when (zerop (mod ln (* 1024 256))) do
(format t "~&~f s | ~d Kb" (/ (- (get-internal-real-time) initial) 1000) (/ ln 1024)))
(values))
(test)
对结果感到困惑,我尝试使用cl-ppcre
- 我不知道我希望什么,但结果非常糟糕......这是我用于测试的代码:
#B
(ql:quickload "cl-ppcre")
(defun test ()
(declare (optimize (debug 0) (safety 0) (speed 3)))
(loop with addidtion = (concatenate 'string "abcdefgh" "efghefgh")
and initial = (get-internal-real-time)
for i from 0 below (+ (* (/ 1024 (length addidtion)) 1024 4) 1000)
for ln = (* (length addidtion) i)
for accumulated = addidtion
then (cl-ppcre:regex-replace-all "efgh" (concatenate 'string accumulated addidtion) "____")
when (zerop (mod ln (* 1024 256))) do
(format t "~&~f s | ~d Kb" (/ (- (get-internal-real-time) initial) 1000) (/ ln 1024)))
(values))
(test)
那么,为了避免一些概括,我决定写自己的,虽然有点幼稚的版本:
#C
(defun replace-all (input match replacement)
(declare (type string input match replacement)
(optimize (debug 0) (safety 0) (speed 3)))
(loop with pattern fixnum = (1- (length match))
with i fixnum = pattern
with j fixnum = i
with len fixnum = (length input) do
(cond
((>= i len) (return input))
((zerop j)
(loop do
(setf (aref input i) (aref replacement j) i (1+ i))
(if (= j pattern)
(progn (incf i pattern) (return))
(incf j))))
((char= (aref input i) (aref match j))
(decf i) (decf j))
(t (setf i (+ i 1 (- pattern j)) j pattern)))))
(defun test ()
(declare (optimize (debug 0) (safety 0) (speed 3)))
(loop with addidtion string = (concatenate 'string "abcdefgh" "efghefgh")
and initial = (get-internal-real-time)
for i fixnum from 0 below (+ (* (/ 1024 (length addidtion)) 1024 4) 1000)
for ln fixnum = (* (length addidtion) i)
for accumulated string = addidtion
then (replace-all (concatenate 'string accumulated addidtion) "efgh" "____")
when (zerop (mod ln (* 1024 256))) do
(format t "~&~f s | ~d Kb" (/ (- (get-internal-real-time) initial) 1000) (/ ln 1024)))
(values))
(test)
几乎一样慢cl-ppcre
!现在,这太不可思议了!我在这里找不到任何会导致性能如此糟糕的东西......而且它仍然很糟糕:(
意识到标准功能迄今为止表现最好,我查看了 SBCL 源代码,经过阅读后我想出了这个:
#D
(defun replace-all (input match replacement &key (start 0))
(declare (type simple-string input match replacement)
(type fixnum start)
(optimize (debug 0) (safety 0) (speed 3)))
(loop with input-length fixnum = (length input)
and match-length fixnum = (length match)
for i fixnum from 0 below (ceiling (the fixnum (- input-length start)) match-length) do
(loop with prefix fixnum = (+ start (the fixnum (* i match-length)))
for j fixnum from 0 below match-length do
(when (<= (the fixnum (+ prefix j match-length)) input-length)
(loop for k fixnum from (+ prefix j) below (the fixnum (+ prefix j match-length))
for n fixnum from 0 do
(unless (char= (aref input k) (aref match n)) (return))
finally
(loop for m fixnum from (- k match-length) below k
for o fixnum from 0 do
(setf (aref input m) (aref replacement o))
finally
(return-from replace-all
(replace-all input match replacement :start k))))))
finally (return input)))
(defun test ()
(declare (optimize (debug 0) (safety 0) (speed 3)))
(loop with addidtion string = (concatenate 'string "abcdefgh" "efghefgh")
and initial = (get-internal-real-time)
for i fixnum from 0 below (+ (* (/ 1024 (length addidtion)) 1024 4) 1000)
for ln fixnum = (* (length addidtion) i)
for accumulated string = addidtion
then (replace-all (concatenate 'string accumulated addidtion) "efgh" "____")
when (zerop (mod ln (* 1024 256))) do
(format t "~&~f s | ~d Kb" (/ (- (get-internal-real-time) initial) 1000) (/ ln 1024)))
(values))
(test)
最后,我能赢,虽然与标准库相比只有一小部分性能——但与几乎所有其他东西相比,它仍然非常非常糟糕......
这是结果表:
| SBCL #A | SBCL #B | SBCL #C | SBCL #D | C gcc 4 -O3 | String size |
|-----------+-----------+------------+-----------+-------------+-------------|
| 17.463 s | 166.254 s | 28.924 s | 16.46 s | 1 s | 256 Kb |
| 68.484 s | 674.629 s | 116.55 s | 63.318 s | 4 s | 512 Kb |
| 153.99 s | gave up | 264.927 s | 141.04 s | 10 s | 768 Kb |
| 275.204 s | . . . . . | 474.151 s | 251.315 s | 17 s | 1024 Kb |
| 431.768 s | . . . . . | 745.737 s | 391.534 s | 27 s | 1280 Kb |
| 624.559 s | . . . . . | 1079.903 s | 567.827 s | 38 s | 1536 Kb |
现在,问题是:我做错了什么?这是 Lisp 字符串固有的东西吗?这可能会通过……什么来缓解?
从长远来看,我什至会考虑编写一个专门的字符串处理库。如果问题不是我的错误代码,而是实现。这样做有意义吗?如果是,你会建议用什么语言来做?
编辑:为了记录,我现在正在尝试使用这个库:https ://github.com/Ramarren/ropes来处理字符串连接。不幸的是,它没有替换功能,并且进行多次替换并不是很简单。但是当我有东西时,我会更新这篇文章。
我尝试稍微改变 huaiyuan 的变体以使用数组的填充指针而不是字符串连接(以实现类似于StringBuilder
Paulo Madeira 建议的东西。它可能可以进一步优化,但我不确定类型 / 哪个方法更快/是否值得重新定义类型*
并+
让它们仅在fixnum
or上操作signed-byte
。无论如何,这是代码和基准:
(defun test/e ()
(declare (optimize speed))
(labels ((min-power-of-two (num)
(declare (type fixnum num))
(decf num)
(1+
(progn
(loop for i fixnum = 1 then (the (unsigned-byte 32) (ash i 1))
while (< i 17) do
(setf num
(logior
(the fixnum
(ash num (the (signed-byte 32)
(+ 1 (the (signed-byte 32)
(lognot i)))))) num))) num)))
(join (x y)
(let ((capacity (array-dimension x 0))
(desired-length (+ (length x) (length y)))
(x-copy x))
(declare (type fixnum capacity desired-length)
(type (vector character) x y x-copy))
(when (< capacity desired-length)
(setf x (make-array
(min-power-of-two desired-length)
:element-type 'character
:fill-pointer desired-length))
(replace x x-copy))
(replace x y :start1 (length x))
(setf (fill-pointer x) desired-length) x))
(seek (old str pos)
(let ((q (position (aref old 0) str :start pos)))
(and q (search old str :start2 q))))
(subs (str old new)
(loop for p = (seek old str 0) then (seek old str p)
while p do (replace str new :start1 p))
str))
(declare (inline min-power-of-two join seek subs)
(ftype (function (fixnum) fixnum) min-power-of-two))
(let* ((builder
(make-array 16 :element-type 'character
:initial-contents "abcdefghefghefgh"
:fill-pointer 16))
(ini (get-internal-real-time)))
(declare (type (vector character) builder))
(loop for i fixnum below (+ 1000 (* 4 1024 1024 (/ (length builder))))
for j = builder then
(subs (join j builder) "efgh" "____")
for k fixnum = (* (length builder) i)
when (= 0 (mod k (* 1024 256)))
do (format t "~&~8,2F sec ~8D kB"
(/ (- (get-internal-real-time) ini) 1000)
(/ k 1024))))))
1.68 sec 256 kB
6.63 sec 512 kB
14.84 sec 768 kB
26.35 sec 1024 kB
41.01 sec 1280 kB
59.55 sec 1536 kB
82.85 sec 1792 kB
110.03 sec 2048 kB