Some thoughts on your benchmark!

Depending on the operating system you're working on, the actual results of your benchmark could be very different. If your benchmark was run on a *nix system, your first call to the subroutine &case1:

print "case1 finds ", &case1, " matches \n";

causes the file to be read and cached by the *nix system. I wasn't sure how perl would or would not benefit from this, but a *nix grep will be able to do pattern matching on the file in cached memory. grep doesn't even have to do a memory to memory copy/move. ( I didn't look at the code, so grep may be doing the memory to memory copy/move. )

I ran you're benchmark on an AIX system, and the results were basically the same as what you saw before. I then modified you're script to call &case2 first, and then &case1 and then &case0 (only once, Benchmark complained!) on a new and un-cached file. The result was that &case0 was the fastest, followed by &case1 and the slowest was &case2(grep). I ran this script on OpenSUSE with similar results. It does appear that perl does get benefit of the caching. If I ran the test again, grep was the winner!

If you're used a *nix system, I hope this gives some idea of why grep looked so much faster than perl.

Note: It's faster to work in memory than on disk.

Further note: You may have to restart the system to guarantee the file isn't cached already. I made this mistake the first time by using a large .gz file that I unzipped, which caused the zipped and unzipped files to be cached.

Thank you

"Well done is better than well said." - Benjamin Franklin

In reply to Re^3: search array for closest lower and higher number from another array by flexvault
in thread search array for closest lower and higher number from another array by bigbot

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