As I understand it a hash is more expensive than an array. Two hashes are more expensive than one hash due to the cost of setting up the buckets. In your case you want to waste some elemets in the array so the answer is GOK. The solution is suck it and see. Run this sort of code and look at real time memory useage. Make either a hash or an array an look at the memory hit.

$size = 20000;

# make a hash
for ($key = 0 ; $key < $size ; $key += 2 ) {
   $hash{$key} = [ ( 0..100 ) ];
}

# make an array, wasting 50% of the spaces
#for ($key = 0 ; $key < $size ; $key += 2 ) {
#   $ary[$key]  = [ ( 0..100 ) ];
#}

print "Made big data structure, sleeping 20 seconds!\n";
sleep 20;
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cheers

tachyon

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