Copy or sever are the Right way to release an old PDL. As you
surmise, if you slice a PDL the original stays around until the slice
gets released. Severing or copying the slice (both do essentially
the same thing) releases the original PDL, which then gets GC'ed by
perl.
Maintaining the connection between two PDLs requires a small but
nonzero bit of overhead, even if the original PDL is an "orphan".
For example, the following is a Bad Idea:
$a = zeroes(1e6+1);
for $i(1..1e6){
$a = $a->(1:);
}
You definitely want to do something like
$a = $a->(1:)->sever;
in the loop instead.
On May 28, 2007, at 8:17 PM, Trevor Carey-Smith wrote:
Hi,
I have a memory usage/garbage collection question. When you
overwrite a piddle with a (smaller) part of itself, what happens to
the original piddle? Is it still in memory? i.e. what happens in
each of the following cases?
perldl> $a = sequence(10)
perldl> $a = $a(0:4)
perldl> $b = sequence(10)
perldl> $b = $b(0:4)->copy
perldl> $c = sequence(10)
perldl> $c = $c(0:4)->sever
Or is there a better way of dropping unwanted parts of a piddle?
Thanks,
Trevor.
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