On 2/6/19 12:44 AM, ToddAndMargo via perl6-users wrote:
On 2/5/19 11:56 PM, ToddAndMargo via perl6-users wrote:
On 2/5/19 8:34 PM, ToddAndMargo via perl6-users wrote:
On Sun, Feb 3, 2019 at 9:36 PM ToddAndMargo via perl6-users
<perl6-users@perl.org <mailto:perl6-users@perl.org>> wrote:
Hi All,
If I have a variable of type Buf which 10000000 bytes in it
and I find the five bytes I want, is it faster, slower,
or no difference in speed to overwrite the same variable
with the five bytes? Or is it faster to put the five bytes
from the first variable into a second variable?
Many thanks,
-T
On 2/5/19 8:42 AM, yary wrote:
There are modules to time two pieces of code and show the difference
https://github.com/perl6-community-modules/perl6-Benchy
https://github.com/tony-o/perl6-bench
You can write up the two versions you're thinking of, feed them to
the benchmark module, and show us what you find!
-y
Hi Yary,
Thank you!
Apparently, overwriting the original buffer only change the
structures pointers, which is almost instantaneous.
And you taught me something new today!
-T
<code VarTest.pl6>
#!/usr/bin/env perl6
use Bench;
my IO::Handle $HaystackHandle = open( "/home/temp/procexp64.exe",
:bin, :ro );
my Buf $Haystack = $HaystackHandle.read( 3000000 );
$HaystackHandle.close;
my Buf $Needle;
my $b = Bench.new;
sub Another() { $Needle = $Haystack.subbuf( 0x14FFAC .. 0x145FAC ); }
sub Same() { $Haystack = $Haystack.subbuf( 0x14FFAC .. 0x145FAC ); }
say "first copies to a new variable; second overwrites the same
variable";
$b.timethese( 100000, {
first => sub { Another; },
second => sub { Same; },
});
</code VarTest.pl6>
$ VarTest.pl6
first copies to a new variable; second overwrites the same variable
Benchmark:
Timing 100000 iterations of first, second...
first: 0.021 wallclock secs (0.021 usr 0.000 sys 0.021 cpu) @
4676612.262/s (n=100000)
second: 0.000 wallclock secs (0.000 usr 0.000 sys 0.000 cpu)
You guys catch my mistake? It is only valid for one iteration.
Chuckle. A rewrite is in order.
<code VarTest.pl6>
#!/usr/bin/env perl6
use Bench;
my IO::Handle $HaystackHandle = open( "/home/temp/procexp64.exe", :bin,
:ro );
my Buf $Haystack = $HaystackHandle.read( 3000000 );
$HaystackHandle.close;
my Buf $SubBuf;
my $b = Bench.new;
sub Another() { my Buf $b = $Haystack; my Buf $Needle = $b.subbuf(
0x14FFAC .. 0x145FAC ); }
sub Same() { my Buf $b = $Haystack; $b = $b.subbuf( 0x14FFAC ..
0x145FAC ); }
say "first copies to a new variable; second overwrites the same variable";
$b.timethese( 100000, {
first => sub { $SubBuf = Another(); },
second => sub { $SubBuf = Same(); },
});
</code VarTest.pl6>
$ VarTest.pl6
first copies to a new variable; second overwrites the same variable
Benchmark:
Timing 100000 iterations of first, second...
first: 0.051 wallclock secs (0.054 usr 0.003 sys 0.057 cpu) @
1965370.177/s (n=100000)
second: 0.052 wallclock secs (0.045 usr 0.001 sys 0.046 cpu) @
1926856.526/s (n=100000)
Virtually no difference
And it would help if I did not reuse variable names.
A little bit of difference:
New variable = 0.053 wallclock secs
Overwrite = 0.085 wallclock secs
<code VarTest.pl6>
#!/usr/bin/env perl6
use Bench;
my IO::Handle $HaystackHandle = open( "/home/temp/procexp64.exe", :bin,
:ro );
my Buf $Haystack = $HaystackHandle.read( 3000000 );
$HaystackHandle.close;
my Buf $SubBuf;
my $b = Bench.new;
sub Another() { my Buf $bb = $Haystack; my Buf $Needle = $bb.subbuf(
0x14FFAC .. 0x145FAC ); }
sub Same() { my Buf $bb = $Haystack; $bb = $bb.subbuf( 0x14FFAC ..
0x145FAC ); }
say "first copies to a new variable; second overwrites the same variable";
$b.timethese( 100000, {
first => sub { $SubBuf = Another(); },
second => sub { $SubBuf = Same(); },
});
</code VarTest.pl6>
$ VarTest.pl6
first copies to a new variable; second overwrites the same variable
Benchmark:
Timing 100000 iterations of first, second...
first: 0.053 wallclock secs (0.052 usr 0.003 sys 0.055 cpu) @
1899696.049/s (n=100000)
second: 0.085 wallclock secs (0.078 usr 0.000 sys 0.078 cpu) @
1180442.430/s (n=100000)
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Computers are like air conditioners.
They malfunction when you open windows
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
