I, for one, would like to see your code for building an 5-byte index?
Storing a million 5-byte integers using 5 million bytes for data, and 44 bytes additional overhead:
my $buffer = "";
my $BYTES = 5;
my $BITS_IN_BYTE = 8;
my $FULL_BYTE = (1 << $BITS_IN_BYTE) - 1;
sub store {
my ($pos, $value) = @_;
for (0 .. $BYTES - 1) {
vec($buffer, $pos * $BYTES + $_, $BITS_IN_BYTE) =
($value >> ($BITS_IN_BYTE * ($BYTES - 1 - $_))) & $FULL_BYT
+E;
}
}
sub fetch {
my ($pos) = @_;
my $sum = 0;
for (0 .. $BYTES - 1) {
$sum <<= $BITS_IN_BYTE;
$sum += vec($buffer, $pos * $BYTES + $_, $BITS_IN_BYTE);
}
$sum;
}
#
# Testing
#
my $TEST_SIZE = 1_000_000;
my @offsets = map {int rand 1 << ($BYTES * $BITS_IN_BYTE)} 1 .. $TEST_
+SIZE;
for (my $i = 0; $i < @offsets; $i++) {
store $i, $offsets[$i];
}
for (my $i = 0; $i < @offsets; $i++) {
my $val = fetch $i;
die unless $val == $offsets[$i];
}
use Devel::Size 'size';
use 5.010;
say "Index size: ", size $buffer;
__END__
Index size: 5000044
Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
Read Where should I post X? if you're not absolutely sure you're posting in the right place.
Please read these before you post! —
Posts may use any of the Perl Monks Approved HTML tags:
- a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
|
For: |
|
Use: |
| & | | & |
| < | | < |
| > | | > |
| [ | | [ |
| ] | | ] |
Link using PerlMonks shortcuts! What shortcuts can I use for linking?
See Writeup Formatting Tips and other pages linked from there for more info.
|
|