There are probably better ways to do what you're doing, but I'm assuming this
is a minimum working example from a more complex use case. If not, you might
like to just do a $table->sumover and then have a look at ran_shuffle in
PDL::GSL::RNG. If would probably accomplish the same thing, but much much
quicker (4 lines, and no for loops). e.g.,
$table = random(10,$size)->rint;
$sums = $table->sumover;
$rng = PDL::GSL::RNG->new('default');
$rng->ran_shuffle($sums); #sums is shuffled in place.
For your code, my guess is that the last row "$table = $table(,$rkeep);" is
causing you trouble. It is generating a new child piddle for every iteration,
but keeping the parent piddle in memory (though now inaccessible, since you
named the new variable the same thing as the parent). All of those slice
operations are being stored (all the way back to the original 10 x 900 piddle.
You may get around this with a call to sever:
$table = $table(,$rkeep)->sever;
Doing that with your code allowed me to push past the segfault limit.
best,
Derek
On Sep 1, 2013, at 10:27 AM, VE wrote:
> Dear All,
>
> I played further with this example
> http://mailman.jach.hawaii.edu/pipermail/perldl/2013-August/008102.html
> and run into the following issue now.
>
> The below code should generate a 2D piddle of random 0 and 1, then take a
> random row, calculate a sum of it, then cut this row off the piddle and do so
> again until there are rows.
>
> I run "out of memory" if the initial piddle has more than 900 rows. In fact,
> I wanted to take a lot more :)
>
> Where is my mistake?
>
> Thank you in advance!
> VE
>
> The code:
> #!/perl
> use strict;
> use warnings;
> use PDL;
> use PDL::NiceSlice;
> use PDL::Math;
> my $size = 900; # the initial number of rows.
> my $table = random 10, $size;
> $table = rint $table;
> my @sums;
> for ( 1 .. $size)
> {
> my ( $col, $row ) = dims $table;
> my $row_x = $row > 1 ? int(rand($row)) : 0;
> my $chosen = $table->dice_axis(1, $row_x);
> push @sums, sum $chosen;
> my $rows_to_remove = pdl($row_x); # rows to be removed
> my $rvals = sequence($table->dim(1)); # all rows indexes
> my $rkeep = setops($rows_to_remove, 'XOR', $rvals); # rows to keep
> $table = $table(,$rkeep);
> }
> # print scalar @sums, $/; # or whatever...
>
>
>
>
>
>
> ---
> [email protected]
> 01.09.2013
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