comment on

Following up on Re: vec overflow? an adjustable example (mini vec tutorial)

#!/usr/bin/perl --
use strict;
use warnings;
use Data::Dump qw/ dd pp /;
my @ints = qw/ 0 0 0 1 1 2 9 11 11 20 22 22 55 /;



#~ my $power     = 8; my $repeat    = 0;
#~ my $power     = 2; my $repeat    = 14;
#~ my $power     = 1; my $repeat    = 28;
my $power     = 3; my $repeat    = 7;

#~ my $power     = 28; my $repeat    = 8; ## (chr(0)x2**28)x8

my $max       = 2**$power;
my $maxminone = $max-1;
my @seen_vecs = ( chr(0) x $max ) x $repeat;;
@seen_vecs = '' unless@seen_vecs ;

dd\@seen_vecs;

print "\n(2**$power=($max)*8=(l@{[$max*8]}))x[$repeat]\n";
print "max bit \@v[$repeat][@{[$max*8]}]\n\n";
my @uniq ;
for my $int( @ints ){
    my $index  = $int >> $power;
    my $offset = $int & $maxminone ;
#~     my $vec = \vec( $seen_vecs[ $int >> $power ], $int & $maxminone
+ , 1);;
    my $vec = \vec( $seen_vecs[ $index ], $offset, 1);;
    next if $$vec ; ## skip if seen ## $seen...[$index]->get( $offset 
+);
    push @uniq, $int;
    $$vec=1;        ## mark as seen ## $seen...[$index]->set( $offset 
+);
    printf "%3u@[%2u][%2u]= %s\n", $int , $index, $offset,unpack('b*',
+ $seen_vecs[ $index ]), ;
    printf "              %s\n", (' ' x $offset ).'^'.$int;
}
dd({ints=>\@ints,uniq=>\@uniq,seen=>\@seen_vecs});
__END__
[download]

The @ in the output it produces is used for meaning of "@at", its not an actual array :) for example 0@[ 0][ 0] means the number zero is stored in the first(zero-th,0-th) seen_vecs string, and its the first bit of the string (0-th bit) ; neat how that works, id-zero is zero-th bit, is offset-th-ed-bit :)

[
  "\0\0\0\0\0\0\0\0",
  "\0\0\0\0\0\0\0\0",
  "\0\0\0\0\0\0\0\0",
  "\0\0\0\0\0\0\0\0",
  "\0\0\0\0\0\0\0\0",
  "\0\0\0\0\0\0\0\0",
  "\0\0\0\0\0\0\0\0",
]

(2**3=(8)*8=(l64))x[7]
max bit @v[7][64]

  0@[ 0][ 0]= 10000000000000000000000000000
              ^0
  1@[ 0][ 1]= 11000000000000000000000000000
               ^1
  2@[ 0][ 2]= 11100000000000000000000000000
                ^2
  9@[ 1][ 1]= 01000000000000000000000000000
               ^9
 11@[ 1][ 3]= 01010000000000000000000000000
                 ^11
 20@[ 2][ 4]= 00001000000000000000000000000
                  ^20
 22@[ 2][ 6]= 00001010000000000000000000000
                    ^22
 55@[ 6][ 7]= 00000001000000000000000000000
                     ^55
{
  ints => [0, 0, 0, 1, 1, 2, 9, 11, 11, 20, 22, 22, 55],
  seen => [
            "\a\0\0\0\0\0\0\0",
            "\n\0\0\0\0\0\0\0",
            "P\0\0\0\0\0\0\0",
            "\0\0\0\0\0\0\0\0",
            "\0\0\0\0\0\0\0\0",
            "\0\0\0\0\0\0\0\0",
            "\x80\0\0\0\0\0\0\0",
          ],
  uniq => [0, 1, 2, 9, 11, 20, 22, 55],
}
[download]

This can help with the vec syntax :) Bit::Vector::Minimal - Object-oriented vec wrapper

In reply to Re^4: DBI::SQLite slowness ( mini vec tutorial ) by Anonymous Monk
in thread DBI::SQLite slowness by Endless

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