Re: Patch to make string-append on win32 100 times faster

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Re: Patch to make string-append on win32 100 times faster

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From:

H.Merijn Brand

Date:

August 2, 2010 04:00

Subject:

Re: Patch to make string-append on win32 100 times faster

Message ID:

20100802130023.4d7dc135@pc09.procura.nl

On Mon, 2 Aug 2010 12:36:04 +0200, demerphq <demerphq@gmail.com> wrote:

> On 31 July 2010 13:44, David Golden <xdaveg@gmail.com> wrote:
> > On Sat, Jul 31, 2010 at 1:14 AM, Eric Brine <ikegami@adaelis.com> wrote:
> >> Theres some perl way to do this without explicitly assigning a large string
> >>>
> >>
> >> It involves open(\$var)
> >
> > Sounds like a new candidate for Scalar::Util.
> 
> Here are three ways to do it in perl. The first is interesting as it
> works slightly differently in that it enables the OOK flag as well,
> which IMO is a bug in substr().

Fourth way is implemented in Data::Peek

$ perl -MDP -e'DDump $_;DGrow $_, 102400; DDump $_'
SV = NULL(0x0) at 0x8301568
  REFCNT = 1
  FLAGS = ()
SV = PV(0x82d1114) at 0x8301568
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x83d7558 ""\0
  CUR = 0
  LEN = 102400

   my $LEN = DGrow ($pv, $size)
       Fastest way to preallocate space for a PV scalar. Returns the allocated
       length. If $size is smaller than the already allocated space, it will
       not shrink.

        cmpthese (-2, {
            pack => q{my $x = ""; $x = pack "x20000"; $x = "";},
            op_x => q{my $x = ""; $x = "x"  x 20000;  $x = "";},
            grow => q{my $x = ""; DGrow ($x,  20000); $x = "";},
            });

                  Rate  op_x  pack  grow
        op_x   62127/s    --  -59%  -96%
        pack  152046/s  145%    --  -91%
        grow 1622943/s 2512%  967%    --

XS code:

void
DGrow (sv, size)
    SV     *sv
    IV      size

  PROTOTYPE: $$
  PPCODE:
    if (SvROK (sv))
        sv = SvRV (sv);
    if (!SvPOK (sv))
        sv_setpvn (sv, "", 0);
    SvGROW (sv, size);
    mPUSHi (SvLEN (sv));
    /* XS DGrow */

> Yves
> 
> $ perl -MDevel::Peek -e'$size=10; $str=" " x $size;
> substr($str,0,$size,""); Dump($str); $str.="ab"; Dump($str);'
> SV = PVIV(0x8ac9fd4) at 0x8ad40c8
>   REFCNT = 1
>   FLAGS = (POK,OOK,pPOK)
>   IV = 10  (OFFSET)
>   PV = 0x8acafa2 ( "          " . ) ""\0
>   CUR = 0
>   LEN = 2
> SV = PVIV(0x8ac9fd4) at 0x8ad40c8
>   REFCNT = 1
>   FLAGS = (POK,pPOK)
>   IV = 0
>   PV = 0x8acaf98 "ab"\0
>   CUR = 2
>   LEN = 12
> $ perl -MDevel::Peek -e'$size=10; $str=" " x $size; $str=~s/.+//g;
> Dump($str); $str.="ab"; Dump($str);'
> SV = PV(0x92b1748) at 0x92d10c0
>   REFCNT = 1
>   FLAGS = (POK,pPOK)
>   PV = 0x92c7f98 ""\0
>   CUR = 0
>   LEN = 12
> SV = PV(0x92b1748) at 0x92d10c0
>   REFCNT = 1
>   FLAGS = (POK,pPOK)
>   PV = 0x92c7f98 "ab"\0
>   CUR = 2
>   LEN = 12
> $ perl -MDevel::Peek -e'$size=10; $str=" " x $size; chop($str) while
> length($str); Dump($str); $str.="ab"; Dump($str);'
> SV = PV(0x928c748) at 0x92ac0d0
>   REFCNT = 1
>   FLAGS = (POK,pPOK)
>   PV = 0x92a2f98 ""\0
>   CUR = 0
>   LEN = 12
> SV = PV(0x928c748) at 0x92ac0d0
>   REFCNT = 1
>   FLAGS = (POK,pPOK)
>   PV = 0x92a2f98 "ab"\0
>   CUR = 2
>   LEN = 12

-- 
H.Merijn Brand  http://tux.nl      Perl Monger  http://amsterdam.pm.org/
using 5.00307 through 5.12 and porting perl5.13.x on HP-UX 10.20, 11.00,
11.11, 11.23, and 11.31, OpenSuSE 10.3, 11.0, and 11.1, AIX 5.2 and 5.3.
http://mirrors.develooper.com/hpux/           http://www.test-smoke.org/
http://qa.perl.org      http://www.goldmark.org/jeff/stupid-disclaimers/

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