[gambit-list] fast csv parser (libcsv wrapped for gambit)
Phil Bewig
pbewig at gmail.com
Sun Feb 11 19:08:31 EST 2007
Wow! I'm both impressed and sad. Impressed at the speed-up. Sad that
something as simple as read-char can be so slow. And I don't find the
fixed-up code nearly as ugly as the C code in libcsv.
Phil
On 2/10/07, Bradley Lucier <lucier at math.purdue.edu> wrote:
>
> OK, I've done a few experiments. I've added
>
> (declare (standard-bindings)(extended-bindings)(block)(fixnum)(not
> safe))
>
> to all files.
>
> Here's the original code on my machine, an Opteron running in 64-bit
> mode, while giving it a 100 MB heap:
>
> > (load "bewig")
> "/export/users/lucier/lang/scheme/csv/bewig.o7"
> > (time (begin (read-all (open-input-file "data.csv") read-csv-
> record) #t))
> (time (begin (read-all (open-input-file "data.csv") read-csv-record)
> #t))
> 591 ms real time
> 580 ms cpu time (497 user, 83 system)
> 2 collections accounting for 29 ms real time (25 user, 4 system)
> 264023440 bytes allocated
> 25865 minor faults
> no major faults
> #t
>
> Next we buffer the collection of characters into a field, (re-)using
> an extensible string (really ugly code at bottom):
>
> > (load "bewig2")
> "/export/users/lucier/lang/scheme/csv/bewig2.o17"
> > (time (begin (read-all (open-input-file "data.csv") read-csv-
> record) #t))
> (time (begin (read-all (open-input-file "data.csv") read-csv-record)
> #t))
> 436 ms real time
> 435 ms cpu time (420 user, 15 system)
> 1 collection accounting for 13 ms real time (13 user, 0 system)
> 45290944 bytes allocated
> 3067 minor faults
> no major faults
> #t
>
> Next we "simply" use macro-read-char from _io.scm instead of read-
> char in the original code:
>
> > (load "bewig+macro-read-char")
> "/export/users/lucier/lang/scheme/csv/bewig+macro-read-char.o2"
> > (time (begin (read-all (open-input-file "data.csv") read-csv-
> record) #t))
> (time (begin (read-all (open-input-file "data.csv") read-csv-record)
> #t))
> 175 ms real time
> 175 ms cpu time (171 user, 4 system)
> 3 collections accounting for 29 ms real time (29 user, 1 system)
> 264030352 bytes allocated
> 376 minor faults
> no major faults
> #t
>
> Finally we use macro-read-char in the ugly, buffered-output code:
>
> > (load "bewig2+macro-read-char")
> "/export/users/lucier/lang/scheme/csv/bewig2+macro-read-char.o2"
> > (time (begin (read-all (open-input-file "data.csv") read-csv-
> record) #t))
> (time (begin (read-all (open-input-file "data.csv") read-csv-record)
> #t))
> 105 ms real time
> 105 ms cpu time (98 user, 7 system)
> no collections
> 45270736 bytes allocated
> 3106 minor faults
> no major faults
> #t
>
> So this is over five times as fast as the original code on this test
> file.
>
> We gain a factor of about three just by inlining the fast path of
> read-char.
>
> Marc, if you don't want Gambit to suck on simple IO processing like
> this, you should use the macro-read-char expansion for read-char in
> the compiler.
>
> Brad
>
> (define (read-csv-record . args)
>
> (define (read-csv sep port)
>
> (define (add-char-to-field c field)
> (let ((length (field-length field))
> (buffer (field-buffer field)))
> (if (< length (string-length buffer))
> (begin
> (string-set! buffer length c)
> (field-length-set! field (+ length 1))
> field)
> (let ((new-buffer (string-append buffer (make-string length))))
> (string-set! new-buffer length c)
> (field-length-set! field (+ length 1))
> (field-buffer-set! field new-buffer)
> field))))
>
> (define (extract-string-from-field! field)
> (let ((result (substring (field-buffer field) 0 (field-length
> field))))
> (reset-field! field)
> result))
>
> (define (new-field)
> (cons (make-string 800)
> 0))
>
> (define (field-buffer field)
> (car field))
>
> (define (field-buffer-set! field value)
> (set-car! field value))
>
> (define (field-length field)
> (cdr field))
>
> (define (field-length-set! field value)
> (set-cdr! field value))
>
> (define (reset-field! field)
> (field-length-set! field 0)
> field)
>
> (define (add-field! field fields)
> (cons (extract-string-from-field! field) fields))
>
>
> (define (start field fields)
> (let ((c (read-char port)))
> (cond ((eof-object? c)
> (reverse fields))
> ((char=? #\return c)
> (carriage-return field fields))
> ((char=? #\newline c)
> (line-feed field fields))
> ((char=? #\" c)
> (quoted-field field fields))
> ((char=? sep c)
> (let ((fields (add-field! field fields)))
> (not-field field fields)))
> (else
> (unquoted-field (add-char-to-field c field) fields)))))
>
> (define (not-field field fields)
> (let ((c (read-char port)))
> (cond ((eof-object? c)
> (cons "" fields))
> ((char=? #\return c)
> (carriage-return '() (add-field! field fields)))
> ((char=? #\newline c)
> (line-feed '() (add-field! field fields)))
> ((char=? #\" c)
> (quoted-field field fields))
> ((char=? sep c)
> (let ((fields (add-field! field fields)))
> (not-field field fields)))
> (else
> (unquoted-field (add-char-to-field c field) fields)))))
>
> (define (quoted-field field fields)
> (let ((c (read-char port)))
> (cond ((eof-object? c)
> (add-field! field fields))
> ((char=? #\" c)
> (may-be-doubled-quotes field fields))
> (else
> (quoted-field (add-char-to-field c field) fields)))))
>
> (define (may-be-doubled-quotes field fields)
> (let ((c (read-char port)))
> (cond ((eof-object? c)
> (add-field! field fields))
> ((char=? #\return c)
> (carriage-return '() (add-field! field fields)))
> ((char=? #\newline c)
> (line-feed '() (add-field! field fields)))
> ((char=? #\" c)
> (quoted-field (add-char-to-field #\" field) fields))
> ((char=? sep c)
> (let ((fields (add-field! field fields)))
> (not-field field fields)))
> (else
> (unquoted-field (add-char-to-field c field) fields)))))
>
> (define (unquoted-field field fields)
> (let ((c (read-char port)))
> (cond ((eof-object? c)
> (add-field! field fields))
> ((char=? #\return c)
> (carriage-return '() (add-field! field fields)))
> ((char=? #\newline c)
> (line-feed '() (add-field! field fields)))
> ((char=? sep c)
> (let ((fields (add-field! field fields)))
> (not-field field fields)) )
> (else
> (unquoted-field (add-char-to-field c field) fields)))))
>
> (define (carriage-return field fields)
> (if (char=? #\newline (peek-char port))
> (read-char port))
> fields)
>
> (define (line-feed field fields)
> (if (char=? #\return (peek-char port))
> (read-char port))
> fields)
>
> (if (eof-object? (peek-char port))
> (peek-char port)
> (reverse (start (new-field) '()))))
>
> (cond ((null? args)
> (read-csv #\, (current-input-port)))
> ((and (null? (cdr args))
> (char? (car args)))
> (read-csv (car args) (current-input-port)))
> ((and (null? (cdr args))
> (port? (car args)))
> (read-csv #\, (car args)))
> ((and (pair? (cdr args)) (null? (cddr args))
> (char? (car args)) (port? (cadr args)))
> (read-csv (car args) (cadr args)))
> (else
> (car '()))))
>
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