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Postings from March 2013
On 26 March 2013 08:32, H.Merijn Brand <h.m.brand@xs4all.nl> wrote:
> On Mon, 25 Mar 2013 20:47:39 -0400, Eric Brine <ikegami@adaelis.com>
> wrote:
>
>> On Sun, Mar 24, 2013 at 4:00 PM, bulk88 <bulk88@hotmail.com> wrote:
>>
>> > Konovalov, Vadim (Vadim)** CTR ** wrote:
>> >
>> >> It was clearly and unambiguously a patch. It wasn't in diff format, but it
>> >>> was clearly indicating that to make your code more portable, you could
>> >>> change the line:
>> >>>
>> >>> HE *hes [count];
>> >>> to
>> >>> #if defined(__BORLANDC__) || defined(_MSC_VER) || defined(__STDC__)
>> >>> HE **hes = Perl_malloc (count * sizeof (HE));
>> >>> #else
>> >>> HE *hes [count];
>> >>> #endif
>> >>>
>> >>
>> >> 1)
>> >> an overlook - it should be HE **hes = Perl_malloc (count * sizeof
>> >> (HE*));
>> >>
>> >> it appears that HE is larger than HE* and allocating more memory, hence
>> >> misbehaviour is not noticed, but anyway, this isn't correct
>> >>
>> >> 2) when that chunk of memory freed? TIA :)
>> >>
>> >
>> > alloca, it can never leak. A non-const length auto C array calls alloca
>> > anyway on C99 under the hood.
>>
>> I think he's asking about the newly introduced Perl_malloc
>
> I tested this yesterday with this code:
> --8<---
> my $n = 100;
> foreach my $f (qw( test1.json test2.json )) {
> say "Testing $f";
> my $jsn = do { open my $fh, "<", $f; local $/; <$fh> };
> printf "Length: %9d\n", length $jsn;
> my $x = decode_json ($jsn);
> printf "Size D: %9d\n", total_size ($x);
> printf "Size E: %9d\n", length encode_json ([$x]);
>
> my $td = 0;
> for (1..$n) {
> my $t0 = [ gettimeofday ];
> $x = decode_json ($jsn);
> $td += tv_interval ($t0);
> }
> printf "%s: decode %10.6f s/run\n", $f, $td / $n;
>
> my $te = 0;
> for (1..$n) {
> my $t0 = [ gettimeofday ];
> my $j = encode_json ([$x]);
> $te += tv_interval ($t0);
> }
>
> printf "%s: encode %10.6f s/run\n", $f, $te / $n;
> }
> -->8---
>
> on two relative big json files test1.json is unformatted (no newlines
> and whitespace) test2.json is formatted (prettied)
>
> -rw-rw-rw- 1 merijn users 716642 Mar 25 18:40 test1.json
> -rw-rw-rw- 1 merijn users 14776790 Mar 25 18:40 test2.json
>
> Testing test1.json
> Length: 716642
> Size D: 2240594
> Size E: 716589
> test1.json: decode 0.010089 s/run
> test1.json: encode 0.003995 s/run
> Testing test2.json
> Length: 14776790
> Size D: 28672598
> Size E: 8198965
> test2.json: decode 0.157494 s/run
> test2.json: encode 0.042437 s/run
>
> Then changed the code to (note the (HE *) and the dropped _ for
> Linux/gcc. Used alloca, not Perl_malloc. I know I should look at
> *en*coding timings only.
>
> #if defined(__BORLANDC__) || defined(_MSC_VER) || defined(__STDC__)
> HE **hes = alloca (count * sizeof (HE *));
> #else
> HE *hes [count]; // if your compiler dies here, you need to enable C99 mode
> #endif
>
> and got
>
> Testing test1.json
> Length: 716642
> Size D: 2240594
> Size E: 716589
> test1.json: decode 0.010471 s/run
> test1.json: encode 0.003938 s/run
> Testing test2.json
> Length: 14776790
> Size D: 28672598
> Size E: 8198965
> test2.json: decode 0.156661 s/run
> test2.json: encode 0.041112 s/run
>
> Then with Perl_malloc
>
> #if defined(__BORLANDC__) || defined(_MSC_VER) || defined(__STDC__)
> HE **hes = Perl_malloc (count * sizeof (HE *));
> #else
> HE *hes [count]; // if your compiler dies here, you need to enable C99 mode
> #endif
>
> which resulted in
>
> Testing test1.json
> Length: 716642
> Size D: 2240594
> Size E: 716589
> test1.json: decode 0.009939 s/run
> test1.json: encode 0.003932 s/run
> Testing test2.json
> Length: 14776790
> Size D: 28672598
> Size E: 8198965
> test2.json: decode 0.157021 s/run
> test2.json: encode 0.041158 s/run
>
> which is still faster than the original code.
>
> gcc (SUSE Linux) 4.7.2 20130108 [gcc-4_7-branch revision 195012]
> This is perl 5, version 16, subversion 3 (v5.16.3) built for i686-linux-64int
> Linux 3.7.10-1.1-desktop [openSUSE 12.3 (Dartmouth)] i386 Core(TM) i7-2620M CPU @ 2.70GHz/800(4) i686 8042 Mb
IMO the differences there are in the noise.
Yves
--
perl -Mre=debug -e "/just|another|perl|hacker/"
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