Question

Running my script through Devel::NYTProf showed that the following portion of code took up the vast majority of running time. The function creates a hash that’s easier to work with, and that hash gets pushed into an array. I’m wondering how this can be done without taking as long as it does.

From Devel::NYTProf:

# Statements | Time on line | Calls | Time in sub
21092   16.4s   21092   273s     push( @events, { create_events_hash($1, $2, $j, @eventHash) } );
# spent 273s making 21092 calls to Parser::create_events_hash, avg 12.9ms/call

# ...                   

# spent 273s (268+4.95) within Parser::create_events_hash which was called 21092 times, 
    avg 12.9ms/call: # 21092 times (268s+4.95s) by 
    Parser::findNewMessages at line 86, avg 12.9ms/call  
# Statements | Time on line 

sub create_events_hash {
    21092   159s            my ( $dateIndex, $msgIDIndex, $eventHashIndex, @eventHash ) = @_;                       

    21092   81.8ms          my %holder;
    21092   137ms           $holder{ID} = $eventHashIndex;
    21092   190ms           $holder{msgDate} = $dateIndex;
    21092   243ms           $holder{ReceivedAt} = $eventHash[$eventHashIndex]{ReceivedAt};
    21092   181ms           $holder{msgID} = $msgIDIndex;
    21092   193ms           $holder{FromHost} = $eventHash[$eventHashIndex]{FromHost};
    21092   187ms           $holder{Priority} = $eventHash[$eventHashIndex]{Priority};

    21092   97.6s           return %holder;
                    }   

Answer 1

For starters, I’d send @eventhash as reference.

push(@events, {create_events_hash($1, $2, $j, \@eventHash)});

It is more effecient this way as it won’t make a copy of the array.