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Re: Perl Hash Performance Hits Brick Wall!by flexvault (Monsignor)
|on Aug 22, 2015 at 09:27 UTC||Need Help??|
I tried to stay out of this one, but 'what the heck!'
The type of work your doing requires a deeper understanding of Perl than you want to spend time on. In your write-up you mention passing a hash from a subroutine back to the main program, but failed to include that in your limited code description. As others have already pointed out, passing a hashref to the subroutine would have avoided having to copy a 27MM key/value hash back to the main program. As you show below it looks like it's in the main program anyway.
But why didn't you build the array while building your hash???
The above code is probably not doing what you think. '@rgb' is not in any specific order. Here's where knowing how Perl allocates an array and a hash, you could have done the following ( untested code ):
At this point you have a hash for telling you the number of colors and an array that represents the exact image in 48 bit increments. By pre-allocating the hash and array you make only one call to the operating system for memory for each, instead of millions of calls.
Spend a little more time learning Perl and using efficient algorithms, and you'll have tools that will make you proud.
"Well done is better than well said." - Benjamin Franklin